A Laboratory Outline for Elementary Organic Chemistry 9781487582999

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A

LABORATORY

OUTLINE

FOR

ELEMENTARY ORGANIC CHEMISTRY

BY

F. R. LORRIMAN,

B.E.M., M.A., Ph.D., F.C.I.C.

AND

J. J. RAE,

M.A., Ph.D., F.C.I.C.

Chemistry Department, University of Toronto

Fourth Edition, Revised

UNIVERSITY

OF

TORONTO

PRESS

FOREWORD THE experiments in this book comprise a series of practical exercises which the authors have found from experience illustrate well the principles of organic chemistry. It is designed to accompany the first course in organic chemistry as given to Preprofessional and General Science students. The authors acknowledge constructive suggestions from Mrs. A. G. Sleep and Dr. Stewart McLean. Students are expected to cover the work assigned for each day. This requires planning and dovetailing of your time. Read through the complete instructions for an experiment before starting it. Experiments marked with an asterisk are lengthy and should be started near the beginning of the period. The symbol ( P) indicates that the product is to be handed in. Time may be saved in writing up an experiment by cutting out the printed instructions and pasting them neatly in your note book. The observations, results and conclusions are then recorded. Tabulate your results wherever possible. Answer all the questions. The analytical balances are not used in this course. Where weighing is required use the triple beam and trip balances provided and weigh to the nearest centigram. Pay particular attention to the amounts and concentrations of the materials to be used. Serious accidents and erroneous observations and conclusions result when incorrect amounts and wrong reagents are used.

COPYRIGHT, CANADA,

1954, 1957, 1959, 1961

BY UNIVERSITY OF TORONTO PRESS PRINTED IN CANADA

1956 1957 THIRD EDITION, 1959 FOURTH EDITION, 1961 REPRINTED,

SECOND EDITION,

REPRINTED WITH ALTERATIONS,

1964

Reprinted in 2018 ISBN 978-1-4875-8171-8 (paper)

CONTENTS EXPERIMENTS

Physical Properties Qualitative Analysis Hydrocarbons Alkyl and Aryl Halides Alcohols Aldehydes and Ketones Carboxylic Acids Salts Esters Phenols and Ethers Fluorescein and Its Derivatives Enols and Quinones High Polymers-Resins and Plastics Molecular Rearrangement Carbohydrates Amines Aniline Dyes Proteins

1-11 12-14 15-24 25-28 29-34

13

21

35-51 52-56 57-60 61-64

43 47

65-73 74-78 79-86

49 53

87-93 94 95-108 109-116 117-120 121-126

Heterocyclic Compounds Identification of Organic Compounds

142

Index

1 9

25 29 39

127-133 134-141

Amides

PAGE

57 61 65 67 75 79 83

85 89 95 99

AVOID ACCIDENTS Wear a laboratory coat to protect your clothes. If you do not wear glasses, wear the GOGGLES provided all the time you are in the laboratory. Keep your desk top clean and dry and free from any unnecessary or extraneous equipment. FIRE RISKS Most organic liquids are flammable and care should be taken if they are heated over an open flame. Small fires in beakers are extinguished by exclusion of air with a wet towel or notebook. Know the location of the fire blanket and the extinguishers. FIRST AID There is a FIRST AID KIT in the storeroom. ( 1) For minor skin bums use ointment. Don't use water. For serious bums go immediately to the Health Service. ( 2) For acid or alkali on skin, wash quickly and thoroughly with water. ( 3) For cuts, wash, disinfect and then bandage. SOME INTERNATIONAL ATOMIC WEIGHTS (Al) (As) (Ba) (Br) (Ca) (C) (Cl) (Cr) (Cu) (F) (H) (I) {Fe)

Aluminum Arsenic Barium Bromine Calcium Carbon Chlorine Chromium Copper Fluorine Hydrogen Iodine Iron

27.0 74.9 137.4 79.7 40.1 12.0 35.5 52.0 63.5 19.0 1.0 126.9 55.9

Lead Lithium Magnesium Manganese Mercury Nitrogen Oxygen Phosphorus Potassium Sodium Sulphur Tin Zinc

(Pb) (Li) (Mg) (Mn) (Hg) (N) (0) (P) (K) (Na) {S) {Sn) {Zn)

207.2 6.9 24.3 54.9 200.6 14.0 16.0 31.0 39.1 23.0 32.1 118.7 65.4

APPROXIMATE CONCENTRATIONS OF SOME LABORATORY REAGENTS Hydrochloric acid Hydrochloric acid Nitric acid Nitric acid Sulphuric acid

{cone.) ( dil.) (cone.) ( dil.) (cone.)

35% 12% 70% 25% 95%

12N 4N 15N 4N 35N

Sulphuric acid Sodium hydroxide Ammonium hydroxide Ammonium hydroxide

{dil.) 15% 4N (reag.) 7% 1.7N (cone.) 28% 7N (dil.) 5% 1.4N

PHYSICAL PROPERTIES 1.

CALIBRATION OF A THERMOMETER

By means of a retort stand and clamp suspend a thermometer fitted through a cork in a small beaker of water. Support the beaker on a wire gauze, so that the bulb of the thermometer is covered by the water, but is 1-2 cm. from the bottom of the beaker. Add a grain of sand, pumice or unglazed porcelain to prevent bumping. When the water is boiling, tabulate the thermometer readings at half-minute intervals for three minutes. Consult the blackboard for the prevailing atmospheric pressure and the relationship between pressure and boiling point of water. Is the correction due to differences in pressure appreciable? Suggest possible causes for any differences that you observe between the thermometer reading and the correct boiling point. What correction must be applied to your thermometer to make its reading correspond to the correct boiling point? Would this correction be applicable at all temperatures? 2.

MELTING POINT

The determination of the melting point is important in the identification of organic substances and as a criterion of their purity. A sharp melting point ( within 1 ° limits) is regarded as indicative of a pure substance, while a "melting range" is caused by the presence of impurities. Prepare some melting point tubes by heating to redness the centre portion of a soft glass test tube and slowly rotating it until it sags. Then remove it from the flame and immediately draw it out until it has an inside diameter of 1-2 mm. Cut this tube into lengths of about 12 cm. and seal each end. Store these in a clean, corked test tube. When required for use, scratch with a file at the centre and sever. Pulverize a small amount of the material whose melting point is to be determined. Introduce sufficient to occupy a length of about 0.5 cm. into the melting point tube. This is accomplished by dipping the open end of the tube into the pulverized substance, then inverting it and causing the adhering particles to fall to the bottom of the tube by drawing a file slowly and gently back and forth across it. Attach the melting point tube by a small rubber band to the lower end of the thermometer or by making use of the principle of capillary action, i.e. wetting the thermometer with water, and bringing the tube in contact with it. The tube will adhere to the thermometer. Suspend the thermometer as in Experiment 1 in a 150 ml. beaker, half full of water, place on an asbestos mat and gradually heat, at the same time stirring the water. Note the temperature at which the substance liquefies. After finding the melting point approximately on the first trial repeat the experiment, heating the water very slowly as you approach the melting point found by the first trial. Record the "sintering" (softening) and the final melting points. 1

3

What liquids would you recommend in which to immerse the melting point tube, if the substance under investigation melted above 100°C? 3. MELTING POINT OF MIXTURES Pulverize and mix well approximately 0.5 g. of naphthalene and 0.2 g. p-dichlorobenzene ( 0.5 g. is approximately the quantity which can be heaped up on a 10¢ coin). Transfer some of the mixture to a melting point tube and heat slowly. Record the temperature at which the mixture first begins to soften and when it has completely liquefied. Write structural formulas for the substances used. When two pure substances are intimately mixed, the melting range of the mixture is lower than that of one, and sometimes lower than that of both of the components. A test for purity frequently used by organic chemists is to mix an authentic sample with the suspected material. If the melting point of the mixture is not lowered, the suspected material is assumed to be identical with the authentic sample. Why does a mixture of thymol and menthol liquefy when triturated? What is meant by "eutectic"? Explain by means of a phase diagram. 0

4. RECRYSTALLIZATION OF AN IMPURE SUBSTANCE (P)

Determine the melting range of the sample of impure acenaphthene or other material provided. Dissolve 3-5 g. in a minimum volume of hot ethanol in a small Erlenmeyer and warm over a hot plate or water bath (KEEP FREE ELAMES AWAY). If the liquid is coloured add a pinch of decolorizing carbon to it (KEEP FLAMES AWAY). Filter hot through a warm wide-stem funnel and allow to cool. If no crystals form when cool, concentrate to ½ volume ( DO NOT EVAPO RATE TO DRYNESS ) and allow to cool again. Attempt to obtain more than one crop of pure crystals. Dry the crystals between pieces of filter paper and then in air for one hour. Take a melting point on some of the powdered dry material. Compare this melting point with the value recorded for pure acenaphthene in the Handbook. Write the formula for acenaphthene. Hand in the purified sample with your name, locker number, name of product and the melting points of the impure and pure products printed clearly on the label. 5. BOILING POINT

(a) Boiling Point of Benzene CAUTION: Benzene vapour is highly flammable and toxic. Fit a thermometer in a test tube by means of a cork in the side of which a groove is cut to permit the escape of vapour. Put about 5 ml. of benzene in the test tube and add a very small piece of unglazed porcelain or a grain of sand to prevent bumping. Adjust the thermometer so that the bulb is in the vapour. Clamp the test tube vertically in a small beaker of water. Heat

5

the water and note the temperature when the benzene is boiling quietly. Record several temperatures at one minute intervals and tabulate your results. Apply the thermometer correction obtained in Experiment 1. Does the temperature change as the benzene evaporates? Explain the significance of a "constant boiling point." Define "Boiling Point" and "Vapour Pressure." The boiling point of pure benzene is recorded as 80.25°C. Account for any difference between this value and the one obtained. In the case of a pure substance, would any difference be observed if the thermometer were in the liquid or the vapour? Discuss. ( b) Micro Boiling Point Use a tube slightly larger in diameter than those required for melting point, sealed at one end. Fill the tube ½ full of benzene by means of a micro pipette, constructed so that its constricted end will fit down into the sealed tube. Withdraw the pipette and replace it by a length of tube longer and smaller in diameter than the boiling point tube, and sealed at the centre instead of at an end. By means of the same set-up as for melting point, ascertain the boiling point of benzene by noting the temperature at which the bubbles issuing from the immersed end of the longer tube increase enormously in size. Obtain another reading by allowing the apparatus to cool and observing the temperature at which the benzene begins to re-enter the hollow tube. Define "boiling point" as an equilibrium process in terms of this method of determination. What is meant by the "vapour pressure" of benzene? 0

6.

FRACTIONAL DISTILLATION

Fit a 250 ml. round bottom Bask with a packed or unpacked distilling column connected by suitably bored corks to a Liebig water condenser. In a cork, previously softened, place a thermometer, so that when the cork and thermometer are inserted into the mouth of the column, the bulb of the thermometer will be at the side arm outlet. Pour into the Bask 50 ml. of the liquid, which is 50% W /W ethyl alcohol the remainder being water and a trace of coloured impurity. Slowly heat the Bask on an asbestos mat, being careful to keep drafts away from the Bask and column. Cooling by drafts can be avoided by "lagging" the column with paper. It is advisable to put ONE piece of pumice or unglazed porcelain into the flask to prevent superheating and bumping. Raise the temperature until the ring of condensing vapour condensate climbs the neck of the column and drops appear on the bottom of the thermometer bulb. The temperature registered by the thermometer at this stage represents the temperature at which the vapor and condensate are in equilibrium. Place a graduated cylinder below the adapter at the open end of the condenser, and record temperature and the volume of condensate at 2 ml. intervals. Keep the conditions as far as possible so that the vapours are refluxing down the column and condensing around the thermometer, and running down the side arm of the column to the condenser. The distillation should proceed at such a rate that not more

7 than 20 drops of distillate per minute collect in the receiver. Return the first 25 ml. of the distillate to the bottle marked "Recovered Ethyl Alcohol." When only about ½ ml. of liquid is remaining in the flask, stop the distillation and when cool, measure the volume of "still residue" plus "column holdback." Draw the distillation curve for the experiment using ml. distillate as the horizontal units and temperatures as the vertical units and draw a smooth curve to pass through the experimental points. Record the "still residue" plus "column holdback," and the loss on distillation, in the diagram. Paste the curve in your notebook and interpret its shape in the light of laboratory information. Make a labelled diagram of the apparatus. Are the temperatures recorded the boiling temperatures of the liquid in the flask? Give reasons. If not, what are they and how could the boiling temperature be ascertained? Could the method used in this experiment be used in ascertaining the boiling point of an aqueous sodium chloride solution? Give reasons for your answer. Could it be used for obtaining the boiling point of chloroform? Give reasons for your answer. Outline concisely the principle of fractional distillation. What is meant by "reflux ratio"? What is its importance? What factors govern the efficiency of a fractionation?

7.

CHROMATOGRAPHIC SEPARATION OF THE COLOURED CONSTITUENTS OF A

Fooo COLOURING SOLUTION

Place about 1 ml. of a very dilute food colour solution in a large test tube. Immerse into it a strip of good grade filter paper about ½ inch in width, so that it acts as a wick. Observe every 10 or 15 minutes over the course of about one hour. Then remove the strip, allow it to dry, and paste it in with your report. Did the food colouring behave as a pure substance? Discuss the results. What is chromatography? Define selective adsorption, RF value.

•s.

CHROMATOGRAPHIC SEPARATION oF PLANT P1GMENTs

Prepare an adsorption column by fitting a one-holed cork with a short glass delivery tube in the bottom of a long piece of large glass tubing ( 1.5 x 25 cm.). Insert a cotton plug above the cork to prevent loss of adsorbent. Fill the tube about two-thirds full of powdered ( 100 mesh) activated alumina. Add 10 ml. of the solution provided to the top of the column. When this has trickled through add 10 ml. of petroleum ether to the column. Comment on the results obtained. 9.

REFRACTOMETRY

This will be illustrated by a class demonstration. Discuss briefly by means of a diagram, the determination of refractive indices and list the uses of these constants in the identification and analysis of organic materials.

9

10. DISTRIBUTION OF A SoLUTE BETWEEN Two IMMISCIBLE SOLVENTS

In a separatory funnel, extract a 15 ml. portion of 0.5% iodine in potassium iodide solution with successive fresh portions of 10 ml. chloroform or carbon tetrachloride secundum artem. To 1 ml. of the aqueous phase after each extraction, add 1 ml. starch suspension. Describe any changes, and continue the extraction process until this colour reaction, which is sensitive for iodine concentrations of the order of 10 parts per million, is negative. Discuss the results. The distribution coefficient of Br2 between water and CS2 is 0.012 at 25°C. If 100 ml. of a 3% aqueous solution of Br2 is shaken once with 100 ml. CS2, how much Br2 is left in the solution? If 100 ml. of a 3% aqueous solution of Br2 is shaken with 50 ml. CS2, the layers separated and the aqueous layer shaken with 50 ml. fresh CS2, how much Br2 is left in the aqueous solution? What conclusions do you draw from these results? 11. EXTRACTION Observe the Soxhlet extractor in operation and draw a labelled diagram explaining how it functions. How is this process used in analytical chemistry? What is the difference in principle between a coffee percolator and a Silex coffee-maker? Describe in about 100 words with diagram one commercial extraction.

QUALITATIVE ANALYSIS 12. TEST FOR CARBON This is the first test to be applied to any unknown substance and the behaviour on ignition may give a surprising amount of information. Is the compound volatile? Does it decompose? Does it leave a non-combustible residue? The odour of gases or vapours should be cautiously noted. Heat gradually small amounts ( i.e. 1 ml. or 1.0 g.) of the following substances in a crucible or on a spatula: (a) ethyl alcohol (ethanol), ( b) glycerol, ( c) sucrose, ( d) carbon tetrachloride, ( e) sodium acetate. Add a few drops of dilute hydrochloric acid to the residue from ( e) and interpret the result. Describe exactly what happens. Charring indicates the presence of carbon. There are many organic substances, however, especially volatile compounds, which do not char under these conditions. Name several. Describe another test which could be used for detecting carbon. NoTE: Metallic elements in organic compounds are generally converted upon ignition into their respective oxides, carbonates, sulphates, etc. These give an ash. What principle permits one to equate the calorific value of sucrose obtained by burning it in a bomb calorimeter to the value obtained in metabolism?

9

10. DISTRIBUTION OF A SoLUTE BETWEEN Two IMMISCIBLE SOLVENTS

In a separatory funnel, extract a 15 ml. portion of 0.5% iodine in potassium iodide solution with successive fresh portions of 10 ml. chloroform or carbon tetrachloride secundum artem. To 1 ml. of the aqueous phase after each extraction, add 1 ml. starch suspension. Describe any changes, and continue the extraction process until this colour reaction, which is sensitive for iodine concentrations of the order of 10 parts per million, is negative. Discuss the results. The distribution coefficient of Br2 between water and CS2 is 0.012 at 25°C. If 100 ml. of a 3% aqueous solution of Br2 is shaken once with 100 ml. CS2, how much Br2 is left in the solution? If 100 ml. of a 3% aqueous solution of Br2 is shaken with 50 ml. CS2, the layers separated and the aqueous layer shaken with 50 ml. fresh CS2, how much Br2 is left in the aqueous solution? What conclusions do you draw from these results? 11. EXTRACTION Observe the Soxhlet extractor in operation and draw a labelled diagram explaining how it functions. How is this process used in analytical chemistry? What is the difference in principle between a coffee percolator and a Silex coffee-maker? Describe in about 100 words with diagram one commercial extraction.

QUALITATIVE ANALYSIS 12. TEST FOR CARBON This is the first test to be applied to any unknown substance and the behaviour on ignition may give a surprising amount of information. Is the compound volatile? Does it decompose? Does it leave a non-combustible residue? The odour of gases or vapours should be cautiously noted. Heat gradually small amounts ( i.e. 1 ml. or 1.0 g.) of the following substances in a crucible or on a spatula: (a) ethyl alcohol (ethanol), ( b) glycerol, ( c) sucrose, ( d) carbon tetrachloride, ( e) sodium acetate. Add a few drops of dilute hydrochloric acid to the residue from ( e) and interpret the result. Describe exactly what happens. Charring indicates the presence of carbon. There are many organic substances, however, especially volatile compounds, which do not char under these conditions. Name several. Describe another test which could be used for detecting carbon. NoTE: Metallic elements in organic compounds are generally converted upon ignition into their respective oxides, carbonates, sulphates, etc. These give an ash. What principle permits one to equate the calorific value of sucrose obtained by burning it in a bomb calorimeter to the value obtained in metabolism?

11

13. SODIUM FUSION TEST FOR NITROGEN, SULPHUR AND HALOGENS ( LASSAIGNE'S TEST) The original method of decomposing organic compounds for identification of the elements involved fusion with sodium. It has now been displaced by a more reliable method-the magnesium-potassium carbonate ignition in the absence of air. However, the former method has been retained here because of its greater simplicity. It is a dangerous procedure unless the instructions are carefullv followed. The oil should be removed from the sodium by means of filte; paper. Do not touch the sodium with the fingers or let it come in contact with water. A small ( 8 x 75 mm.) soft glass test tube is used as the fusion tube. In a fume hood support in a beaker, a large test tube ( 2.5 x 15 cm.) one-third filled with water, with the mouth of the tube pointing toward the back of the hood. (GOGGLES!). Then put a pellet of clean, dry sodium about the size of a pea into the bottom of the fusion tube and on the sodium drop a small amount of the material sufficient to cover the end of a pen-knife blade. Warm the tube carefully until all of the material appears to be decomposed, and then heat to redness. While the tube is still red-hot, plunge it into the test tube of water, taking care that your face is protected from any pieces of burning sodium which may be thrown from the surface of the water. When all the excess sodium has reacted, pour the liquid into a beaker and bring it to a boil. Filter the solution and keep the :filtrate for the following tests. If the original substance contained any of the following elements, in what form would they be present in the filtrate? ( N, S, Cl, Br, I) (a) Test for Nitrogen (P) To the filtrate, add 2 ml. of freshly prepared 10% ferrous sulphate and shake the contents of the tube. Then add 2 ml. of a 5% ferric salt solution, shaking the contents of the tube well, and bring it to a boil. Cool, acidify with dilute sulphuric acid (litmus). Set the tube aside for about half an hour and observe from time to time. A precipitate of Prussian Blue will be formed at once if considerable nitrogen was present in the material tested, while if present in small proportions, a greenish blue solution will result from which the Prussian Blue will only settle out on several hours standing. If the first test is negative, do the fusion again, using larger quantities of the material. Label the test tube containing the result of the test, and hand it in. Write the equations for the reactions involved in the above test. Write the formula for caffeine and calculate the percentage of nitrogen in caffeine. NoTE: A few nitrogen compounds decompose at low temperatures, with the liberation of free nitrogen, and fail to form sodium cyanide when fused with sodium. ( b) Test for Sulphur Perform a fusion as in 13. Proceed as follows with two separate aliquots of the fusion :filtrate. ( i) Acidify 5 ml. of the filtrate with dilute nitric acid (litmus) and add

13

2--3 drops of lead acetate reagent. A brown or black precipitate indicates sulphur. Write equations. (ii) To 5 ml. of the filtrate add 2 drops of freshly prepared sodium nitroprusside solution. A deep reddish colouration indicates sulphur. Sometimes the colour is violet and of short duration. Write equations.

( c) Test f01' Halogens Perform a fusion as in 13. Test a 5 ml. aliquot of the fusion filtrate in the following manner: Acidify with dilute nitric acid and boil to expel hydrogen sulphide and hydrogen cyanide, if present. Add 2-4 drops of 1% silver nitrate reagent. A precipitate indicates the presence of a halogen. If the precipitate is white and readily soluble in ammonium hydroxide the halogen is probably chlorine alone. Silver bromide and silver iodide are usually yellow. If specific halogen is to be identified the method is outlined in texts and should be read. Usually there is enough information available from various sources to render this latter identification superfluous. 14. BEILSTEIN TEST FOR HALOGENS

Coil a 12 in. length of copper wire about a pencil. Heat carefully this piece of coiled copper wire for a few seconds. Cool the wire, dip it into a portion of the substance to be tested and heat again. Perform this test with separate portions of toluene, chloroform, chlorobenzene, amyl bromide and hexane. Discuss the results.

HYDROCARBONS 15. PREPARATION OF ETHYLENE

BY THE

DEHYDRATION OF ETHANOL

WARNING: Ethylene and air, when mixed in almost any proportions, form explosive mixtures. Keep all Hames away! In an apparatus which is already set up and operating, ethylene ( ethene) is being generated by running ethyl alcohol into cone. H2SO4 or pyrophosphoric acid at 220°C under which conditions the ethyl alcohol breaks up intramolecularly into ethylene and water and intermolecularly into diethyl ether and water. The ethylene is freed of carbon dioxide by bubbling it through sodium hydroxide solution, after which it is collected by displacement of water. Collect two 250 ml. Erlenmeyers full of ethylene. Stopper the flasks and do the following tests: (i) Cautiously smell some of the gas. Observe its similarity to chloroform. (ii) To one flask add 10 ml. of a cold, dilute neutral solution of potassium permanganate ( 0.05%) and shake well. Explain the result. This is the Baeyer test for unsaturation.

13

2--3 drops of lead acetate reagent. A brown or black precipitate indicates sulphur. Write equations. (ii) To 5 ml. of the filtrate add 2 drops of freshly prepared sodium nitroprusside solution. A deep reddish colouration indicates sulphur. Sometimes the colour is violet and of short duration. Write equations.

( c) Test f01' Halogens Perform a fusion as in 13. Test a 5 ml. aliquot of the fusion filtrate in the following manner: Acidify with dilute nitric acid and boil to expel hydrogen sulphide and hydrogen cyanide, if present. Add 2-4 drops of 1% silver nitrate reagent. A precipitate indicates the presence of a halogen. If the precipitate is white and readily soluble in ammonium hydroxide the halogen is probably chlorine alone. Silver bromide and silver iodide are usually yellow. If specific halogen is to be identified the method is outlined in texts and should be read. Usually there is enough information available from various sources to render this latter identification superfluous. 14. BEILSTEIN TEST FOR HALOGENS

Coil a 12 in. length of copper wire about a pencil. Heat carefully this piece of coiled copper wire for a few seconds. Cool the wire, dip it into a portion of the substance to be tested and heat again. Perform this test with separate portions of toluene, chloroform, chlorobenzene, amyl bromide and hexane. Discuss the results.

HYDROCARBONS 15. PREPARATION OF ETHYLENE

BY THE

DEHYDRATION OF ETHANOL

WARNING: Ethylene and air, when mixed in almost any proportions, form explosive mixtures. Keep all Hames away! In an apparatus which is already set up and operating, ethylene ( ethene) is being generated by running ethyl alcohol into cone. H2SO4 or pyrophosphoric acid at 220°C under which conditions the ethyl alcohol breaks up intramolecularly into ethylene and water and intermolecularly into diethyl ether and water. The ethylene is freed of carbon dioxide by bubbling it through sodium hydroxide solution, after which it is collected by displacement of water. Collect two 250 ml. Erlenmeyers full of ethylene. Stopper the flasks and do the following tests: (i) Cautiously smell some of the gas. Observe its similarity to chloroform. (ii) To one flask add 10 ml. of a cold, dilute neutral solution of potassium permanganate ( 0.05%) and shake well. Explain the result. This is the Baeyer test for unsaturation.

15

(iii) To the other flask add 10 ml. of bromine water and shake well. Explain the results of (ii) and (iii) and write equations for the reactions. Write the equation for the preparation of ethylene. Draw a labelled diagram of the generating apparatus. Give another general method for preparing unsaturated hydrocarbons, also a general method for the preparation of saturated hydrocarbons. Write equations for the steps involved in the commercial preparation of acetylene from limestone and coal and from petrochemicals. 16.

TESTS FOR UNSATURATION

(a) Bromine Test To 2 ml. samples of hexane, amylene ( 1-pentene ), benzene, cyclohexane, cyclohexene and gasoline (white) add drop by drop 1 ml. of a 5% solution of bromine in carbon tetrachloride and shake. Count the drops added and note changes produced after each drop. The reaction may be considered complete after 5 minutes. Tabulate and explain the results obtained. Write the equation for the reaction with amylene. ( b) Permanganate Test ( Baeyer's) To 2 ml. of each of the above substances add 2 ml. of 5% sodium carbonate solution and then drop by drop 1 ml. of N/10 potassium permanganate solution. Shake well after each addition. Explain the results and write an equation for the reaction with cyclohexene. Describe tests, one for each, that could be used to distinguish between ( i) ethene and ethyne, (ii) ethene and benzene. 0

17.

TOTAL DECARBOXYLATION OF A SALT-PREPARATION OF BENZENE (P)

Intimately mix 3~ test tube dry sodium benzoate with 3~ test tube calcium hydroxide. Transfer this to a large Pyrex test tube ( about 15 x 2.5 cm. ) clamped at an angle of about 30° and fitted with a bent glass delivery tube at least 12 inches long, dipping into a test tube which in turn is standing in a beaker of ice cold water. Have an instructor inspect your apparatus. Heat the powder highly, running the flame up and down the tube so that the heat will be uniformly distributed as long as distillate is forming. Show that the distillate contains benzene by nitrating 2 ml. of the product using the procedure described in Experiment 22 for the nitration of nitrobenzene. A colour reaction by mixing a small amount of the crude dinitro product with 5 ml. acetone to which has been added 1 ml. 10% NaOH, shows the presence of m-dinitrobenzene (red). If the test is positive recrystallize 0.5 g. of the material from the smallest amount of ethanol required to dissolve it. Hand in the recrystallized DNB with M.P. recorded on the label. Write the equation for the reaction and indicate what would have resulted had the sodium benzoate been pyrolyzed without the addition of the calcium hydroxide ( Exp. 58).

17 18.

TEST FOR

AROMATIC

HYDROCARBONS-FORMATION

OF

HALOCHROMIC

SALTS

To two portions of 2 ml. of dry chloroform in two dry test tubes, add respectively, one drop of benzene and a few flakes of naphthalene. Mix thoroughly and incline the test tube so as to moisten the wall. Then, to each liquid, add about 0.5 g. powdered anhydrous AbC16 so that some of the powder strikes the side of the test tube. Note immediately the colour of the powder which has come in contact with the liquid, also the colour of the liquid. These colours are characteristic of aromatic hydrocarbons and are called "halochromic salts." 19.

SELF-ALKYLATION OF AN AROMATIC-THE FRIEDEL-CRAFTS REACTION ( p)

In a 100 ml. dry Erlenmeyer flask gradually mix 0.2 g. ( catalytic portions) anhydrous pellets of freshly powdered AlCls with 3 ml. benzyl chloride in 10 ml. CS2. Keep the system at room temperature in a fume hood. Swirl the contents from time to time, and hold the open mouth of a bottle of ammonium hydroxide to the end of the calcium chloride tube occasionally. When the evolution of hydrogen chloride becomes brisk, swirl the contents frequently and if they become semi-solid, add 5 ml. carbon disulphide, swirl or mix with a stirring rod to make uniform, repeat swirling frequently and set away in a fume hood until the following laboratory period. When the CS2 has completely evaporated, add 5 ml. dilute HCl and 25 ml. water and allow to stand in order to decompose the AlCls complex. Finally detach the solid product from the flask by means of a nichrome spatula, filter, air-dry and hand in. The chief product is 9, 10-dihydroanthracene. Indicate how it is formed and outline the mechanism. Alkylation represents the original type of Friedel-Crafts' reaction. The reaction has subsequently been very greatly extended in its scope. 20.

PREPARATION OF ANTHRACENE P1cRATE (P)

Most polynuclear hydrocarbons form sharp-melting, coloured adducts with picric acid. These "picrates" frequently serve as a means of identifying the hydrocarbons in question. In an evaporating dish, away from flames place 0.2 g. anthracene and 30 ml. of a 2% solution of picric acid in ethanol. Stir occasionally and set aside until the next laboratory period, allowing it to evaporate to dryness in the air. Hand in the product, properly labelled. Write the formulas for anthracene and for picric acid. 21.

PREPARATION OF NITROBENZENE

WARNING: Aromatic nitro- and amino-compounds are very toxic and readily cause cyanosis. Some people are peculiarly susceptible to even small amounts of these, and hence extreme care should be taken when working with them. Benzene itself is toxic and should be handled as such. If any of these compounds gets on the skin, it should be washed off immediately with ethyl alcohol.

19

Mix very carefully in an Erlenmeyer about 15 ml. of concentrated sulphuric acid and 20 ml. concentrated nitric acid. (GOGGLES!) To this mixture add, drop by drop, with constant shaking, 5.0 ml. of benzene. The contents of the flask must never get hot, and great care must be taken that the acid does not splash on the flesh or clothing. When all of the benzene has been added, shake for a few minutes, and then pour into about 300 ml. water. Observe the oily phase which separates out. Might it be only unchanged benzene? Why? Write the equation for the reaction and calculate the yield of nitrobenzene expressed as a percentage of the theoretical. Remove the water from this product by means of a filter paper. Save the product for Experiment 22. Densities: Benzene =0.9 g/ml. Nitrobenzene =1.2 g/ml. Cone. nitric acid (70% HNOs) =1.4 g/ml. If the nitration has proceeded too far, a yellow precipitate of metadinitrobenzene will be obtained. Consult a demonstrator in this case. What was the function of the sulphuric acid in this reaction? Outline a suitable mechanism for the process. 22. PREPARATION OF DINITROBENZENE (P) (FUME HOOD!) Into a dry 50 ml. Erlenmeyer place 5 ml. concentrated sulphuric acid and then cautiously (GOGGLES!) add, about 1 ml. at a time, 9 ml. of Fuming nitric acid (HNOs = 95%, density= 1.5 g./ml.). Now add to the mixed acids thus prepared, 3 ml. of nitrobenzene, which you have prepared in the previous experiment. Heat for 10 minutes shaking frequently (CAUTION) in a beaker of boiling water and then CAREFULLY pour while hot, with stirring (GOGGLES!) into 200 ml. of ice-water. Allow to cool, filter on a small Buchner funnel, wash free of acid and allow to dry in the air. When dry, weigh and calculate the yield. Determine the M.P. of the product, label, and hand in. Predict the structure of the bulk of the dinitrobenzene formed and write the equation for the reaction. What explanation is given for the fact that nitro groups are metadirecting and deactivating? Comment on the difference in the conditions required to obtain the mono- and the dinitro compounds. 23. REDUCTION OF NITRO COMPOUNDS

In a 10 x 1.2 cm. test tube with a tight-fitting cork place 2 drops of nitrobenzene. Half fill the tube with 5% alcoholic potassium hydroxide solution and then add 5% stabilized ferrous ammonium sulphate solution until the test tube is filled to within 1 cm. of the bottom of the cork. Run a control experiment omitting the nitrobenzene. Shake both tubes vigorously for about one minute. Explain the results. List with names three monomolecular reduction products of nitrobenzene.

21 24.

FORMATION OF AN AROMATIC FREE RADICAL ( SCHMIDLIN'S EXPERIMENT) ( p)

In a small Erlenmeyer with tight-fitting cork, dissolve 1 g. triphenyl chloromethane ( triphenylmethyl chloride) in 25 ml. benzene. Note the colour. Then add 3 g. zinc dust. Cork tightly and shake vigorously for several minutes. Allow the solid phase to settle, and decant about 5 ml. of the supernatant liquid into a test tube. Dilute with 5 ml. benzene and divide into two equal portions. To one portion add 10 drops of 1% iodine solution in benzene. Explain all colour changes. Shake the second portion so that air mixes with the liquid for several minutes. Allow to stand for about five minutes, observing closely. Decant 20 ml. of the remaining supernatant liquid into a small Erlenmeyer, shake it with air until the colour of the free radical has been discharged to a light yellow. Filter off the crystals of peroxide. Dry these crystals between filter papers and hand in. Write equations.

ALKYL AND ARYL HALIDES 25.

REACTION OF HALIDES WITH SILVER NITRATE

To 2 ml. of alcoholic silver nitrate solution in four separate test tubes add 5 drops of bromoform, chlorobenzene, n-propyl chloride, and benzyl chloride respectively. Shake the tubes well at intervals of 5 minutes for 15 minutes. To another 1 ml. of each of these halides add 2 ml. of reagent sodium hydroxide and boil for 5 minutes. Cool the solution and acidify to litmus with nitric acid. Add to each 2 ml. of alcoholic silver nitrate. Explain the results obtained. 26.

RATE OF HYDROLYSIS OF HALIDES

To 5 ml. of water in each of five test tubes add 2 drops of bromocresolgreen indicator solution. To these tubes add 4 drops of primary butyl chloride, secondary butyl chloride, chlorobenzene, tertiary butyl chloride and benzyl chloride respectively. Shake all the tubes and immediately place them in a water bath at 60°C. Note the colour before adding the chloride and at half-minute intervals thereafter for 5 minutes. Bring to a boil and heat for a further 5 minutes. Bromocresol-green is yellow at pH 3.8 and blue at pH 5.4. Draw conclusions regarding the relative rates of hydrolysis. Give a reasonable explanation for it. Write equations. Describe a reaction of alkyl halides in which this order of reactivity is reversed. Give alternative names for the reagents and products resulting from the above reactions using the I.U.C. system. Name the alcohols as derivatives of carbinol (methanol).

21 24.

FORMATION OF AN AROMATIC FREE RADICAL ( SCHMIDLIN'S EXPERIMENT) ( p)

In a small Erlenmeyer with tight-fitting cork, dissolve 1 g. triphenyl chloromethane ( triphenylmethyl chloride) in 25 ml. benzene. Note the colour. Then add 3 g. zinc dust. Cork tightly and shake vigorously for several minutes. Allow the solid phase to settle, and decant about 5 ml. of the supernatant liquid into a test tube. Dilute with 5 ml. benzene and divide into two equal portions. To one portion add 10 drops of 1% iodine solution in benzene. Explain all colour changes. Shake the second portion so that air mixes with the liquid for several minutes. Allow to stand for about five minutes, observing closely. Decant 20 ml. of the remaining supernatant liquid into a small Erlenmeyer, shake it with air until the colour of the free radical has been discharged to a light yellow. Filter off the crystals of peroxide. Dry these crystals between filter papers and hand in. Write equations.

ALKYL AND ARYL HALIDES 25.

REACTION OF HALIDES WITH SILVER NITRATE

To 2 ml. of alcoholic silver nitrate solution in four separate test tubes add 5 drops of bromoform, chlorobenzene, n-propyl chloride, and benzyl chloride respectively. Shake the tubes well at intervals of 5 minutes for 15 minutes. To another 1 ml. of each of these halides add 2 ml. of reagent sodium hydroxide and boil for 5 minutes. Cool the solution and acidify to litmus with nitric acid. Add to each 2 ml. of alcoholic silver nitrate. Explain the results obtained. 26.

RATE OF HYDROLYSIS OF HALIDES

To 5 ml. of water in each of five test tubes add 2 drops of bromocresolgreen indicator solution. To these tubes add 4 drops of primary butyl chloride, secondary butyl chloride, chlorobenzene, tertiary butyl chloride and benzyl chloride respectively. Shake all the tubes and immediately place them in a water bath at 60°C. Note the colour before adding the chloride and at half-minute intervals thereafter for 5 minutes. Bring to a boil and heat for a further 5 minutes. Bromocresol-green is yellow at pH 3.8 and blue at pH 5.4. Draw conclusions regarding the relative rates of hydrolysis. Give a reasonable explanation for it. Write equations. Describe a reaction of alkyl halides in which this order of reactivity is reversed. Give alternative names for the reagents and products resulting from the above reactions using the I.U.C. system. Name the alcohols as derivatives of carbinol (methanol).

23

27. HALOFORM REACTION-loDOFORM TEST Most aldehydes and ketones whose formulas contain the acetyl group, or substances that may be readily oxidized to aldehydes or ketones that meet with the above requirement will give chloroform or bromoform or iodoform if they are warmed with hypochlorites, hypobromites or hypoiodites, respectively. Since iodoform is easily detected, its formation is the basis of a test for such structures. In four separate test tubes place respectively 5 ml. of 5% solution of acetone in water, 5 ml. of 1% solution of ethyl alcohol in water, 5 ml. of a 2% solution of isopropyl alcohol, and 5 ml. of 2% methyl ethyl ketone in water. To each add 3 ml. reagent sodium hydroxide solution, and then 5 ml. of 10% solution of iodine in potassium iodide. Note the odour and the colour of the iodoform precipitated. Filter off all the iodoform formed and allow it to dry in the air on the filter paper until the next laboratory period. Then carefully heat some in a test tube for a few seconds, and hold a moistened strip of starch-paper at the mouth of the test tube. Conclusions? Perform the iodoform test on 5% aqueous solutions of methanol, ethyl acetate, diethyl ketone and acetic acid and explain the results. Even when the iodoform does not precipitate, its odour is nevertheless sufficiently distinctive to serve as a test. "'28. PREPARATION OF CHLOROFORM (P) Set up a 1000 ml. distillation apparatus, but do not for the present connect the distillation flask with the condenser. Use a solid cork to stopper the mouth of the distillation flask. Have the adapter dipping into a 25 ml. graduated cylinder tube two-thirds full of cold water, standing in a beaker half filled with cold water, to prevent as much as possible of the chloroform distillate from evaporating. Take 50 g. of calcium hypochlorite ( HTH) ( a 50 ml. beaker full) and 400 ml. water. Mix the solid hypochlorite with part of the water in a beaker and pour into the distilling flask, rinsing the contents of the beaker into the flask with the remainder of the water and washing down anything adhering to the neck of the flask. Then carefully add 10 ml. of acetone a little at a time, shaking the contents of the flask after each addition and cooling if necessary. If the flask heats up considerably, cool under the tap. When all of the acetone has been added connect the distilling flask with the condenser and carefully heat the flask. If frothing commences, withdraw the flame until the reaction subsides, then heat again until no more oily drops of chloroform condense. Measure the volume of the crude chloroform, saving the aqueous layer of the distillate. Using the densities of the acetone ( 0.8 g./ml.) and of chloroform ( 1.5 g./ml.) calculate the yield of chloroform, based upon the acetone used. Test 10 ml. of the aqueous layer of the distillate by the iodoform test to ascertain whether any acetone distilled over unchanged. Result? Can you account for the fact that 100% yield of chloroform was not obtained?

25 Write the equations for the preparation. Test the solubility of some of the chloroform in water. Is it miscible in all proportions? Does it give chloride ion? Hand in the remainder of the product with the yield stated on the label.

ALCOHOLS 29.

PREPARATION OF ETHYL ALCOHOL BY FERMENTATION OF GLUCOSE

Take 20 ml. of 50% glucose solution ( diluted corn syrup), and dilute to 100 ml. with water. Make a paste by triturating 0.5 g. of yeast with 10 ml. of water. Pour the glucose solution, together with 5 ml. of tomato juice and 10 ml. of Pasteur salts solution ( potassium or calcium phosphates, magnesium sulphate and ammonium tartrate) plus the yeast suspension into a 250 ml. Erlenmeyer flask provided with a tight-fitting cork and glass delivery tube, bent at right angles. Fill a second flask about one-third full of clear lime water, and add 10 ml. of kerosene to form a layer over the lime water. By means of a piece of rubber tubing, and another piece of glass tubing bent at right angles, have the delivery tube from the first flask dipping into the lime water. Allow the apparatus to stand several days at about 37°C., and then dismantle it and examine the lime water. Add 10 ml. dilute hydrochloric acid to the lime water. Transfer about 50 ml. of the brew to a small distilling flask and distil off about 10 ml. of this liquid and test for ethyl alcohol by the iodoform test. Write the empirical equation for the formation of ethyl alcohol from glucose. What were the functions of the various ingredients of the brew? Why was the lime water covered by a layer of kerosene? What other reactions might have been going on along with the alcoholic fermentation? What is the necessity for keeping such a system sterile as far as other organisms are concerned? Read concerning enzymes, fermentation, yeast, brewers' wort, proofspirit, alcohol content of liquors. Write the formulas for inositol, thiamin and pantothenic acid; three of the B complex vitamins found in tomato juice and necessary for the normal growth of yeast. 30.

ACTION OF ACTIVE METALS ON ALCOHOLS

( i) To 5 ml. of methanol add one of the freshly cut small pieces of sodium or lithium provided. What reaction takes place? Equation? Taking care that no unused metal remains; dilute the liquid with an equal volume of water and test with litmus. Equation? (ii) Dissolve 10 drops cyclohexanol in 5 ml. dry benzene and then add a small clean piece of sodium or potassium or lithium. Shake and observe from time to time over a period of about 5 minutes. Write the equation. DESTROY ALL UNCHANGED ACTIVE METAL BY ADDING METHANOL OR ETHANOL

Torri Write the equation for the reaction between a divalent metal such as calcium and cyclohexanol.

25 Write the equations for the preparation. Test the solubility of some of the chloroform in water. Is it miscible in all proportions? Does it give chloride ion? Hand in the remainder of the product with the yield stated on the label.

ALCOHOLS 29.

PREPARATION OF ETHYL ALCOHOL BY FERMENTATION OF GLUCOSE

Take 20 ml. of 50% glucose solution ( diluted corn syrup), and dilute to 100 ml. with water. Make a paste by triturating 0.5 g. of yeast with 10 ml. of water. Pour the glucose solution, together with 5 ml. of tomato juice and 10 ml. of Pasteur salts solution ( potassium or calcium phosphates, magnesium sulphate and ammonium tartrate) plus the yeast suspension into a 250 ml. Erlenmeyer flask provided with a tight-fitting cork and glass delivery tube, bent at right angles. Fill a second flask about one-third full of clear lime water, and add 10 ml. of kerosene to form a layer over the lime water. By means of a piece of rubber tubing, and another piece of glass tubing bent at right angles, have the delivery tube from the first flask dipping into the lime water. Allow the apparatus to stand several days at about 37°C., and then dismantle it and examine the lime water. Add 10 ml. dilute hydrochloric acid to the lime water. Transfer about 50 ml. of the brew to a small distilling flask and distil off about 10 ml. of this liquid and test for ethyl alcohol by the iodoform test. Write the empirical equation for the formation of ethyl alcohol from glucose. What were the functions of the various ingredients of the brew? Why was the lime water covered by a layer of kerosene? What other reactions might have been going on along with the alcoholic fermentation? What is the necessity for keeping such a system sterile as far as other organisms are concerned? Read concerning enzymes, fermentation, yeast, brewers' wort, proofspirit, alcohol content of liquors. Write the formulas for inositol, thiamin and pantothenic acid; three of the B complex vitamins found in tomato juice and necessary for the normal growth of yeast. 30.

ACTION OF ACTIVE METALS ON ALCOHOLS

( i) To 5 ml. of methanol add one of the freshly cut small pieces of sodium or lithium provided. What reaction takes place? Equation? Taking care that no unused metal remains; dilute the liquid with an equal volume of water and test with litmus. Equation? (ii) Dissolve 10 drops cyclohexanol in 5 ml. dry benzene and then add a small clean piece of sodium or potassium or lithium. Shake and observe from time to time over a period of about 5 minutes. Write the equation. DESTROY ALL UNCHANGED ACTIVE METAL BY ADDING METHANOL OR ETHANOL

Torri Write the equation for the reaction between a divalent metal such as calcium and cyclohexanol.

27 31. HALOGENATION OF ALCOHOLS Add 7 ml. of Lucas Reagent ( cone. HCl - ZnCl2) to 1 ml. of each of the following alcohols; primary butyl (normal), secondary butyl and tertiary butyl. Shake well, set aside and observe carefully over a period of about fifteen minutes. The alkyl chlorides of these alcohols are insoluble in aqueous media and the progress of their formation can be noted by the opalescence imparted to the systems and the subsequent separation of the halide as a discrete phase. List the alcohols in order of their reactivity in this reaction and write the equations for the reactions. Discuss the mechanism of the reactions. Compare your results with those of Experiment 26 when the reverse process was considered. 32. RELATIVE OXIDATION RATES OF ALCOHOLS Place 10 drops of normal butyl, secondary butyl and tertiary butyl alcohols respectively in each of three test tubes. Add to each 5 ml. dilute sulphuric acid, and then 5 ml. of 0.1 N. potassium permanganate solution. Shake at frequent intervals. Observe the time required for the decolorization of the permanganate in each case and thence compare their relative oxidation rates. If unable under these conditions to differentiate between any particular pair, devise and perform a modified experiment which will enable you to decide. 33. OxrnATION OF A PRIMARY ALCOHOL-PREPARATION OF AcETALDEHYDE In a 125 ml. distilling flask, place 10 g. powdered potassium or sodium dichromate, and add a solution of 40 ml. water and 40 ml. dilute sulphuric acid. CAUTIOUSLY add 25 ml. of 50% aqueous ethanol, about 5 ml. at a time, with careful shaking, and cooling in running water if necessary. This reaction is exothermic, and care should be taken to prevent the dichromate from forming a cake at the bottom. Stopper the flask with a cork, connect to a condenser, the adapter of which is dipping into a 50 ml. Erlenmeyer half filled with cold water, supported in a beaker of cold water. Distill. Acetaldehyde boils at 20°C., and on distilling over will dissolve in the water, giving an aqueous solution of acetaldehyde. After distillation has proceeded for about five minutes, cork up the receiver, allow the liquid in the distilling flask to cool, and then observe its colour. What does this colour indicate? Write the equation for the reaction, in two parts, using the hypothetical equation representing the oxidizing value of a dichromatesulphuric solution plus the equation for the oxidation of ethanol by available oxygen. Keep the aqueous solution of acetaldehyde for future experiments (35, 41, 47). 0

34. OXIDATION OF A SECONDARY ALCOHOL-PREPARATION OF ACETONE Oxidize a 6 ml. portion of 2-propanol using the same procedure and quantities as outlined for the oxidation of a primary alcohol ( Exp. 33). 0

29 Keep the distillate and later test for the presence of acetone. ( Iodofonn and nitroprusside test.) Write the complete equation for the oxidation. To perform the nitroprusside test, add 1 ml. freshly prepared solution of sodium nitroprusside ( a small crystal of nitroprusside dissolved in about 3 ml. water) to 1 ml. of solution under test. Make alkaline with sodium hydroxide solution. A red colour is produced if acetone is present. For other experiments in which alcohols play a part see Experiments 15, 53, 59, 61, and 62. 34A. PREPARATION OF 3,5-DINITROBENZOATE OF ETHYL ALCOHOL Reflux together for fifteen minutes 0.5 g. of 3,5-dinitrobenzoyl chloride, 1 ml. of ethanol, and 1 ml. of pyridine in 5 ml. of benzene. Allow the benzene to evaporate and cool the residue. Add 10 ml. of 5% NaHCO3 solution and stir. Remove the product by suction filtration, wash with a little NaHCO3. Determine its m.p.

ALDEHYDES AND KETONES 35. TESTS FOR ALDEHYDES (a) Schiff's Test Schiff's reagent is prepared by decolorizing a 1% aqueous solution of Fuchsine (Magenta) or Rosaniline with sulphur dioxide. When properly prepared it should be water-white. It should be kept in an amber bottle and must be used in the cold, and in the absence of alkalies. To each of seven test tubes, add 5 ml. Schiff's reagent. To one test tube add 10 drops of your prepared acetaldehyde solution ( Exp. 33); to the second 10 drops of formalin; to the third 5 drops of acetone; to the fourth 5 drops of methyl ethyl ketone; to the fifth 5 drops of a 10% alcoholic solution of phenylacetaldehyde; to the sixth 3 drops of acetophenone; and keep the seventh as a control. Observe during the first five minutes, and again at the end of one hour. ( b) Fehling's Test Fehling's solution is made by dissolving copper sulphate in water, designating this solution as "Fehling's Solution A," and then dissolving sodium hydroxide and Rochelle salt in water and designating this as "Fehling's Solution B." Equal quantities of "A" and "B'' are mixed together as required. Make ready a beaker half full of boiling water. Into each of seven test tubes place 5 ml. combined Fehling's solutions (A+ B ). To each of the tubes add, respectively, the materials listed in 35 (a) and keep the seventh as a control. Immerse these in the boiling water, and heat for about five minutes. Write the equations for the reaction of the aldehydes with Fehling's assuming that the active part of Fehling's is cupric hydroxide. Tabulate the results of both Experiments 35 (a) and ( b).

29 Keep the distillate and later test for the presence of acetone. ( Iodofonn and nitroprusside test.) Write the complete equation for the oxidation. To perform the nitroprusside test, add 1 ml. freshly prepared solution of sodium nitroprusside ( a small crystal of nitroprusside dissolved in about 3 ml. water) to 1 ml. of solution under test. Make alkaline with sodium hydroxide solution. A red colour is produced if acetone is present. For other experiments in which alcohols play a part see Experiments 15, 53, 59, 61, and 62. 34A. PREPARATION OF 3,5-DINITROBENZOATE OF ETHYL ALCOHOL Reflux together for fifteen minutes 0.5 g. of 3,5-dinitrobenzoyl chloride, 1 ml. of ethanol, and 1 ml. of pyridine in 5 ml. of benzene. Allow the benzene to evaporate and cool the residue. Add 10 ml. of 5% NaHCO3 solution and stir. Remove the product by suction filtration, wash with a little NaHCO3. Determine its m.p.

ALDEHYDES AND KETONES 35. TESTS FOR ALDEHYDES (a) Schiff's Test Schiff's reagent is prepared by decolorizing a 1% aqueous solution of Fuchsine (Magenta) or Rosaniline with sulphur dioxide. When properly prepared it should be water-white. It should be kept in an amber bottle and must be used in the cold, and in the absence of alkalies. To each of seven test tubes, add 5 ml. Schiff's reagent. To one test tube add 10 drops of your prepared acetaldehyde solution ( Exp. 33); to the second 10 drops of formalin; to the third 5 drops of acetone; to the fourth 5 drops of methyl ethyl ketone; to the fifth 5 drops of a 10% alcoholic solution of phenylacetaldehyde; to the sixth 3 drops of acetophenone; and keep the seventh as a control. Observe during the first five minutes, and again at the end of one hour. ( b) Fehling's Test Fehling's solution is made by dissolving copper sulphate in water, designating this solution as "Fehling's Solution A," and then dissolving sodium hydroxide and Rochelle salt in water and designating this as "Fehling's Solution B." Equal quantities of "A" and "B'' are mixed together as required. Make ready a beaker half full of boiling water. Into each of seven test tubes place 5 ml. combined Fehling's solutions (A+ B ). To each of the tubes add, respectively, the materials listed in 35 (a) and keep the seventh as a control. Immerse these in the boiling water, and heat for about five minutes. Write the equations for the reaction of the aldehydes with Fehling's assuming that the active part of Fehling's is cupric hydroxide. Tabulate the results of both Experiments 35 (a) and ( b).

31 36.

SENSITIVITY OF THE SCHIFF TEST

Take 1 ml. formalin ( 35% W /V formaldehyde) and dilute to 100 ml. with water. Shake well and then dilute 1 ml. of this solution to 100 ml. with water. Dilute 1 ml. of this second diluted solution in like manner to give a third diluted solution. Then to 2 ml. Schiff's reagent in each of three separate test tubes add respectively 5 ml. of each of the diluted solutions. Allow to stand for 1 hour, and then comment upon the sensitivity of the Schiff test for formaldehyde in terms of parts per million formaldehyde content detectable. This is the basis of the Jephcott method for the quantitative estimation of minute concentrations of formaldehyde, and hence of methanol. 0

37.

REDUCTION OF A KETONE TO A SECONDARY ALCOHOL-PREPARATION OF DIPHENYL CARBINOL ( p)

In a 125 ml. flask with wide mouth place 3 g. benzophenone and 75 ml. 10% alcoholic potassium hydroxide solution. Add 12 g. zinc dust, connect the flask to a reflux condenser and boil gently for 2 hours. Filter by decantation into a large evaporating dish or beaker while hot, add 25 ml. water, stir, evaporate to about 15 ml. total volume and set aside covered with a watch glass until next laboratory period. Filter off the crystals, wash with 10 ml. 50% water-alcohol, then with 50 ml. water, 10 ml. at a time, dry and hand in the product. What was the purpose of the final addition of water and the subsequent evaporation? 38.

PREPARATION OF ALDEHYDES BY CATALYTIC OXIDATION OF ALCOHOLS

In two test tubes, place respectively, 10 drops of methanol and 10 drops of ethanol. Warm the alcohols slightly so that the test tubes will be filled with their vapours. Prepare a coil of copper wire by winding the wire around a pencil about half a dozen times. Heat the coil to redness by holding it for a few seconds in the upper oxidizing part of the Bunsen flame, withdraw it, and note its appearance. To what is the appearance due? Then heat it again as before, and while still at red heat, plunge it into the tube filled with the alcohol vapour. Note carefully the appearance of the wire, especially the part which was near the top of the test tube, smell the contents of each test tube, add a few ml. of Schiff's reagent to each tube and allow to stand for about five minutes. Conclusions? Write equations for the reaction between the wire and the alcohols. Look up the commercial preparation of formaldehyde, and indicate the reaction by equations. 39.

PREPARATION oF AcROLEIN FROM GLYCEROL BY DEHYDRATION

Place about 3 drops of glycerol and 1 g. calcined anhydrous potassium bisulphate in an evaporating dish. Heat the system cautiously with stirring; smell the gaseous products and hold a strip of filter paper, moistened with Schiff's reagent, close to the top of the dish. Discuss the results and write an

33

equation for the reaction. What is the I.U.C. name for acrolein? Why is the acrolein test useful for detection of vegetable oils and fats? Acrolein is a lachrymator. Give the names and formulas of two other lachrymators. 40.

RESORCINOL TEST FOR FORMALDEHYDE

Dilute 5 drops of formalin to 10 ml. with water, add 5 drops of 1% aqueous solution of resorcinol and shake. Pour this liquid cautiously down the side of a second test tube containing about 3 ml. of concentrated sulphuric acid. Observe the colour at the interface of the aqueous and the acid layers. This colour is thought to be due to a compound formed by the interaction of the formaldehyde with the resorcinol with elimination of water, and constitutes a very delicate test. Repeat the test with methanol. Write the formula of resorcinol. Give it an alternative name. Write the formulas and names for the dihydric phenols which are isomeric with resorcinol. 41.

ACTION OF A BAsE ON AcETALDEHYDE TO FoRM A REsIN

Boil 10 ml. of your prepared acetaldehyde solution ( Exp. 33) with 10 drops of 40% sodium hydroxide solution. Note the appearance and odour of the product which is thought to be formed by the aldol reaction and subsequent dehydration and polymerization. Write the equation for the aldol reaction of acetaldehyde, also the dehydration of the aldol. Give the I.U.C. names for the products at each stage. 0

42.

ALDOL REACTION-PREPARATION OF

2, 6-DIBENZALCYCLOHEXANONE

(P)

In a 125 ml. Erlenmeyer place 2.0 ml. cyclohexanone ( density = 1.0 g./ml.). Add 4.0 ml. benzaldehyde (density= 1.0 g./ml.). Then add 15 ml. reagent sodium hydroxide solution, 15 ml. water and 15 ml. ethanol. Warm under reflux over a beaker of boiling water for 2 hours, shaking occasionally. Then set aside until the next laboratory period to allow the product to crystallize. Filter and wash by decantation with two portions of 5 ml. cold 50% methanol-water then with cold water until almost neutral in reaction. Allow the product to dry, weigh it and calculate the yield. Hand it in properly labelled. Write the equation for the reaction in stages and account for the fact that the product is coloured. List the structural necessities for the aldol-type of reaction and outline the mechanism. Write the equations for the aldol-type reaction between (a) benzaldehyde and acetone and ( b) benzaldehyde and acetophenone and name the products. What will be the formulas and names of the substances formed on dehydration of these products? 43.

POLYMERIZATION OF FORMALDEHYDE (P)

Place 5 ml. formalin in an evaporating dish and leave until the next laboratory period. The solid product is paraformaldehyde. In a test tube, place sufficient of the polymer to cover the bottom of

35 the tube. Carefully heat this and hold a strip of filter paper moistened with Schiff's reagent at the mouth of the tube. Record all observations and explain the results. Depolymerization by heat is a common property of addition polymers. Hand in the remainder of the product properly labelled. 0

44.

PREPARATION OF HEXAMETHYLENETETRAMINE (P)

Mix 10.0 ml. formalin with 20.0 ml. of 28% ammonium hydroxide in an evaporating dish and evaporate to dryness in a fume chamber, by placing the dish over the mouth of a beaker half filled with water which is boiling, or on a steam bath. As the liquid thickens, it must be stirred occasionally. Dry well until the solid becomes powdery. Weigh the dry product to within 0.1 g., write the equation for the reaction, and calculate your yield, assuming that the formalin contains 35% W /W of formaldehyde, and has a density of 1.0 g./ml. and that the ammonium hydroxide also has a density of 1.0 g./ml. Give another name for hexamethylenetetramine. Hand in the product and when it is returned to you, put it away stoppered for a future experiment ( 89). From a consideration of the Kekule model of hexamine, comment upon its symmetry. How is the super-explosive RDX prepared from hexamine? 45.

ADDITION REACTION OF KETONES WITH SODIUM BISULPHITE

To 3 ml. of acetone, add 4 ml. of a cold freshly prepared concentrated solution of sodium bisulphite and shake vigorously. Is heat evolved? What else is observed? Repeat the test using 1 ml. cyclohexanone instead of acetone. Write the equation for the reaction. Name two other important reagents which form addition compounds with aldehydes and ketones and write the equations for the reaction of each of these reagents with acetaldehyde and with acetone. Outline the mechanism of such reactions. 46.

REACTION OF ALDEHYDES AND KETONES WITH HYDRAZINE

(a) To separate 5 ml. portions of freshly prepared alcoholic 2,4-dinitrophenylhydrazine reagent add respectively about 5 drops of ( i) benzaldehyde and (ii) acetaldehyde drop by drop. Shake and warm. Observe the crystals that form when cooled. ( b ) In a test tube add 5 drops of acetophenone to 10 ml. of a 1% solution of 2,4-dinitrophenylhydrazine (DNPH) in 95% ethanol. Warm in a beaker of boiling water and allow to evaporate to about half volume. Then allow to cool. What is the substance formed? Equation? 47.

RELATIVE OXIDATION RATES OF SOME ALDEHYDES AND KETONES

Into each of five test tubes place 5 ml. N/10 potassium permanganate and 5 ml. dilute sulphuric acid. To the first test tube add 10 drops formalin,

37 to the second 10 drops of your prepared acetaldehyde solution ( Exp. 33), to the third 5 drops acetone, to the fourth 5 drops cyclohexanone, and to the fifth, a few crystals of benzophenone. Any tubes which do not decolorize after five minutes at room temperature should be warmed in a beaker half full of boiling water. Arrange these five substances in order of ease of oxidation under these conditions and account for any differences. Write the equation for oxidation of acetone using the hypothetical equation representing the oxidizing value of permanganate with sulphuric acid. What products would result on a similar oxidation of hexanone-2 and of cyclohexanone? 48.

AUTO-OXIDATION OF BENZALDEHYDE

At the first of the laboratory period, make a smear of a couple of drops of benzaldehyde on a watch glass. Place a piece of starch-iodide paper which has been moistened with water, in contact with the smear. Observe at the end of an hour and then at the end of the laboratory period. Explain what is observed. Write an equation for the reaction. Perbenzoic acid (benzoyl hydrogen peroxide) which is formed here is an active oxidizer. Write the formula for peracetic acid. 0

49.

PREPARATION OF THE OXIME OF

VANILLIN ( p)

In a small Erlenmeyer place 2.0 g. hydroxylamine hydrochloride in 20 ml. methanol. Add 1.0 g. vanillin and then 4 ml. reagent sodium hydroxide solution plus 10 ml. water and warm on a water bath at 60° for about½ hour. Transfer to an evaporating dish and allow to stand until the next laboratory period, about two-thirds covered by a watch glass so that the mother-liquor will be in contact with the solid product. Filter off the oxime, wash twice with 10 ml. of water, dry in the air, weigh, and hand in. Does it possess the fragrance of vanillin? By means of suitable structures, represent the type of isomerism possible in vanillin oxime.

·so.

REDucTioN oF A KEToNE To A D1TERTIARY ALcoaoL-PREPARATION oF TETRAMETHYL PINACOL ( p)

N.B. The success of this experiment depends upon anhydrous conditions.

In a dry 125 ml. flask surmounted by a tight-fitting water-reflux, place 2 g. dry magnesium turnings and 20 ml. dry benzene and clamp over a water bath. Then add through the condenser, about 3 ml. at a time, 15 ml. of a 20% solution of mercuric chloride in dry acetone. If the reaction does not commence within a few minutes of the addition of the first portion as evidenced by a vigorous ebullition, warm the flask carefully on a water bath and be ready to cool it with running water should the reaction become too vigorous. Once the reaction has commenced, it is rarely necessary to supply further heat. Add the remainder of the mercuric chloride solution at such a rate

39 that the reaction is as vigorous as possible and yet under control. After the addition of the mercuric chloride solution, add while still refluxing, a solution of 5 ml. dry acetone and 5 ml. dry benzene, and when the reaction slows down, reflux on a water bath for one hour. During this period the magnesium pinacolate which has been formed, swells up into a grayishwhite spongy mass. This should be shaken vigorously from time to time over the period of another half-hour refluxing. Then add through the condenser, 6 ml. water+ 6 ml. ordinary benzene and heat again on the water bath for half an hour with occasional shaking. This hydrolyses the magnesium pinacolate to pinacol which passes into the benzene solution. What is the precipitate which forms at this stage? Pour off the supernatant liquid through a filter paper, keeping as much as possible of the solid in the flask and extract this solid residue hot by refluxing for about 5 minutes with a further portion of 12 ml. ordinary benzene. Filter this hot and add it to the first :filtrate. Distil the combined extracts to half of the original volume to remove most of the acetone. Transfer the still-residue to a widemouth flask, add 6 ml. water and shake vigorously. Cool in an ice bath and set away until the next laboratory period, well stoppered. Filter off the pinacol hydrate and dry as well as possible by pressing carefully between layers of filter paper. Hand in the crude pinacol hydrate, carefully stoppered. On receiving it back, put it away carefully for a future experiment ( Exp. 94). What is formed on the intramolecular dehydration of pinacol? Write the structure and name for the pinacol which would be formed in a similar manner from benzophenone. 51.

PREPARATION OF THE SEMICARBAZONE OF C1NNAMIC ALDEHYDE (P)

In a small Erlenmeyer, dissolve 2.0 g. semicarbazide hydrochloride and 2.0 g. hydrated sodium acetate in 40 ml. water + 25 ml. ethanol. Then with vigorous shaking and stirring add slowly 1 ml. cinnamic aldehyde ( density = 1.1 g./ml. ). Warm on a water bath for about 5 minutes with occasional gentle shaking, then place the Erlenmeyer in an ice bath for about 10 minutes. Filter off the product, allow to air-dry and hand in. Does the product possess the fragrance of cinnamic aldehyde? Discuss by structural references, the type of isomerism possible in the product. Tabulate, with formulas and names, the ammonia derivatives which react with the carbonyl portion of aldehydes and ketones. Give the general type-formula of each product formed, and state the importance of these reactions.

CARBOXYLIC ACIDS 52.

EFFECT OF ALPHA-HALOGEN SUBSTITUTION ON THE STRENGTH OF CARBOXYLIC Acrns

To separate 5 ml. portions of IN acetic and IN trichloroacetic acids, add 1-3 drops of Methyl Violet [pH 0-2 (yellow to blue)]. Look up the degrees of ionization of these acids. What generality is illustrated here? What electronic explanation is given for the difference observed?

39 that the reaction is as vigorous as possible and yet under control. After the addition of the mercuric chloride solution, add while still refluxing, a solution of 5 ml. dry acetone and 5 ml. dry benzene, and when the reaction slows down, reflux on a water bath for one hour. During this period the magnesium pinacolate which has been formed, swells up into a grayishwhite spongy mass. This should be shaken vigorously from time to time over the period of another half-hour refluxing. Then add through the condenser, 6 ml. water+ 6 ml. ordinary benzene and heat again on the water bath for half an hour with occasional shaking. This hydrolyses the magnesium pinacolate to pinacol which passes into the benzene solution. What is the precipitate which forms at this stage? Pour off the supernatant liquid through a filter paper, keeping as much as possible of the solid in the flask and extract this solid residue hot by refluxing for about 5 minutes with a further portion of 12 ml. ordinary benzene. Filter this hot and add it to the first :filtrate. Distil the combined extracts to half of the original volume to remove most of the acetone. Transfer the still-residue to a widemouth flask, add 6 ml. water and shake vigorously. Cool in an ice bath and set away until the next laboratory period, well stoppered. Filter off the pinacol hydrate and dry as well as possible by pressing carefully between layers of filter paper. Hand in the crude pinacol hydrate, carefully stoppered. On receiving it back, put it away carefully for a future experiment ( Exp. 94). What is formed on the intramolecular dehydration of pinacol? Write the structure and name for the pinacol which would be formed in a similar manner from benzophenone. 51.

PREPARATION OF THE SEMICARBAZONE OF C1NNAMIC ALDEHYDE (P)

In a small Erlenmeyer, dissolve 2.0 g. semicarbazide hydrochloride and 2.0 g. hydrated sodium acetate in 40 ml. water + 25 ml. ethanol. Then with vigorous shaking and stirring add slowly 1 ml. cinnamic aldehyde ( density = 1.1 g./ml. ). Warm on a water bath for about 5 minutes with occasional gentle shaking, then place the Erlenmeyer in an ice bath for about 10 minutes. Filter off the product, allow to air-dry and hand in. Does the product possess the fragrance of cinnamic aldehyde? Discuss by structural references, the type of isomerism possible in the product. Tabulate, with formulas and names, the ammonia derivatives which react with the carbonyl portion of aldehydes and ketones. Give the general type-formula of each product formed, and state the importance of these reactions.

CARBOXYLIC ACIDS 52.

EFFECT OF ALPHA-HALOGEN SUBSTITUTION ON THE STRENGTH OF CARBOXYLIC Acrns

To separate 5 ml. portions of IN acetic and IN trichloroacetic acids, add 1-3 drops of Methyl Violet [pH 0-2 (yellow to blue)]. Look up the degrees of ionization of these acids. What generality is illustrated here? What electronic explanation is given for the difference observed?

41 0

53. OXIDATION oF AN ALCOHOL TO AN Acm-PREPARATION OF BENZOic Acm (P)

In a 250 ml. Erlenmeyer, surmounted by a water condenser, add, in the order given, 8 g. powdered KMnO4, 150 ml. reagent dilute H2SO4 and 2 ml. benzyl alcohol. Heat for about two hours under reflux and then cool the flask and contents in ice-water. Is there any odour of benzaldehyde at this stage? Filter by suction and suck partly dry while in the Buchner, but do not wash. Divide this moist crude filter cake into approximately two equal portions. Air-dry one portion thoroughly. Purify the moist portion by recrystallization from the minimum amount of boiling water. If the solution is coloured, cool and add a pinch of decolourizing charcoal and heat again. Purify the dry portion by sublimation over a low flame from an evaporating dish with funnel inverted over it. Write the complete equation for the oxidation. Hand in the two purified portions separately, properly labelled. 54. SuscEPTIBILITY OF ACETIC Acrn TO OXIDATION Boil together for a minute in a small Erlenmeyer, 10 drops of 50% acetic acid, 5 ml. water, 1 ml. dilute H2SO4, with N/10 KMnQ4 solution added dropwise as long as it is being decolorized. What conclusions can be drawn regarding the susceptibility of the carboxyl group and of the saturated hydrocarbon residue toward oxidation? 55. RELATIVE EASE OF OXIDATION OF SOME CARBOXYLIC Acms Add a pinch or a few drops of the following acids to 5 ml. water then add 5 ml. dilute sulphuric acid to each. To make the next operation as nearly simultaneously as possible, use batches of five acids at a time. Add I ml. N/10 permanganate to each, shake at intervals, and observe. Carry on the observations over a 10 minute period. The acids to be used are: cinnamic, citric, formic, furoic ( pyromucic), gallic, lactic, mandelic, oleic, oxalic, phenylacetic, phthalic, salicylic, stearic, succinic, tartaric. Tabulate the results showing ( 1) name of acid, ( 2) structural formula, ( 3) relative ease of oxidation, ( 4) portion of structure susceptible to oxidation. 0

56. INCREASING THE CARBON CHAIN LENGTH BY nm CYANOHYDRIN REA.cTION-PREPARATION OF MANDELIC Acm (P)

N.B. From the time that the POTASSIUM CYANIDE is added this preparation must be carried out in a fume hood. Care must be taken not to inhale the fumes and the hands must be thoroughly washed with soap and water after this experiment and any time during it if any of the liquid gets on them. In a 100 ml. beaker place 10.0 g. of sodium bisulphite and dissolve it in 25 ml. of cold water. To this add slowly with stirring 6.0 ml. of benzalde-

43

hyde ( density = 1.09 g. /ml.). Stir the system vigorously for 5 minutes at room temperature and then for 5 minutes in an ice bath. What is the formula for the product at this stage? Filter and allow to drain for 5 minutes but do not attempt to clean the solid from the beaker completely. Transfer the solid from the filter paper back to the original beaker and wash it down with not more than 25 ml. of water. Stir this into a uniform paste and add, with stirring, 15.0 ml. of freshly prepared 30% potassium cyanide solution. Stir for 5 minutes and separate the oily product ( Formula?) from the bulk of the aqueous phase by transferring the system to a large test tube and stirring well until the oil has risen to the top. Pour off the oil into a large evaporating dish. Add 25 ml. of cone. hydrochloric acid to hydrolyse the nitrile ( cyanohydrin) and bring to a boil. Allow to boil gently and stir occasionally until the oil has disappeared and crystals are forming around the edge of the container. Adjust the total volume to approx. 30 ml. Pour the system into a 100 ml. beaker, chill in an ice bath, cover with a watch glass and set aside until the next laboratory period. Filter off the crude product, air-dry, calculate the yield and hand it in. Write the equations for all the reactions involved and name the products at the various stages. 56A. PREPARATION OF ANILIDE OF ACETIC Acm Mix 1 ml. of acetic acid with 2 ml. of thionyl chloride and reflux for thirty minutes. Cool the mixture and add 2 ml. aniline in 20 ml. of benzene. Warm the mixture for five minutes. Decant the benzene solution, evaporate and determine the m.p. of the residue. Equation?

SALTS 57. SOLUBILITY OF SOME SALTS OF CARBOXYLIC Acrns Place sufficient benzoic acid to cover the bottom of a test tube in each of four test tubes. To one of these add 5 ml. reagent NaOH solution, to the second 5 ml. of 5% NH40H solution, to the third, 5 ml. of 5% Na2C03 solution, and to the fourth, 5 ml. of water and record your observations. Write equations for the reactions. Prepare four more test tubes and in each of these add sufficient benzoic acid to cover the bottom and then add 5 ml. 5% NH40H to each. Boil until no more fumes of NH3 can be detected by smell ( THIS IS IMPORTANT!). To the first test tube add 2 ml. of 5% CuS04 solution. To the second add 2 ml. of 5% CaCb solution. To the third add 2 ml. 5% Pb ( NQ3) 2 solution. To the fourth add concentrated HCl until distinctly acidic. Write equations for the reactions involved. If benzoic acid is characteristic of carboxylic acids having both hydrophylic and hydrophobic portions, what generalizations can you draw about solubilities of the salts of such acids in water? Compare the solubilities of the sodium, potassium and ammonium salts with the solubility of the free acid in water.

43

hyde ( density = 1.09 g. /ml.). Stir the system vigorously for 5 minutes at room temperature and then for 5 minutes in an ice bath. What is the formula for the product at this stage? Filter and allow to drain for 5 minutes but do not attempt to clean the solid from the beaker completely. Transfer the solid from the filter paper back to the original beaker and wash it down with not more than 25 ml. of water. Stir this into a uniform paste and add, with stirring, 15.0 ml. of freshly prepared 30% potassium cyanide solution. Stir for 5 minutes and separate the oily product ( Formula?) from the bulk of the aqueous phase by transferring the system to a large test tube and stirring well until the oil has risen to the top. Pour off the oil into a large evaporating dish. Add 25 ml. of cone. hydrochloric acid to hydrolyse the nitrile ( cyanohydrin) and bring to a boil. Allow to boil gently and stir occasionally until the oil has disappeared and crystals are forming around the edge of the container. Adjust the total volume to approx. 30 ml. Pour the system into a 100 ml. beaker, chill in an ice bath, cover with a watch glass and set aside until the next laboratory period. Filter off the crude product, air-dry, calculate the yield and hand it in. Write the equations for all the reactions involved and name the products at the various stages. 56A. PREPARATION OF ANILIDE OF ACETIC Acm Mix 1 ml. of acetic acid with 2 ml. of thionyl chloride and reflux for thirty minutes. Cool the mixture and add 2 ml. aniline in 20 ml. of benzene. Warm the mixture for five minutes. Decant the benzene solution, evaporate and determine the m.p. of the residue. Equation?

SALTS 57. SOLUBILITY OF SOME SALTS OF CARBOXYLIC Acrns Place sufficient benzoic acid to cover the bottom of a test tube in each of four test tubes. To one of these add 5 ml. reagent NaOH solution, to the second 5 ml. of 5% NH40H solution, to the third, 5 ml. of 5% Na2C03 solution, and to the fourth, 5 ml. of water and record your observations. Write equations for the reactions. Prepare four more test tubes and in each of these add sufficient benzoic acid to cover the bottom and then add 5 ml. 5% NH40H to each. Boil until no more fumes of NH3 can be detected by smell ( THIS IS IMPORTANT!). To the first test tube add 2 ml. of 5% CuS04 solution. To the second add 2 ml. of 5% CaCb solution. To the third add 2 ml. 5% Pb ( NQ3) 2 solution. To the fourth add concentrated HCl until distinctly acidic. Write equations for the reactions involved. If benzoic acid is characteristic of carboxylic acids having both hydrophylic and hydrophobic portions, what generalizations can you draw about solubilities of the salts of such acids in water? Compare the solubilities of the sodium, potassium and ammonium salts with the solubility of the free acid in water.

45 ,58.

PARTIAL DECARBOXYLATION OF A SALT-PREPARATION OF ACETONE

Half fill an 8 inch test tube with dry calcium acetate. Using set-up described in Experiment 17 heat highly and uniformly. Divide the distillate into two parts and test for the presence of acetone by ( i) the iodoform test and (ii) the nitroprusside test ( Exp. 34). To a few grams of the powder remaining in the reaction tube, add about 10 ml. dilute hydrochloric acid. Conclusions? Write an equation for the chemical reactions involved in the pyrolysis. Compare this equation with that for the total decarboxylation of a salt (Exp. 17). 0

59.

PREPARATION AND REACTIONS OF A SOAP

In a 125 ml. Erlenmeyer, fitted with a reflux condenser, place about 2 g. of fat or oil provided and 30 ml. of 5% alcoholic potassium hydroxide solution. Reflux until the glyceride is completely saponified ( about 40 minutes) and then pour the product into an evaporating dish and allow to cool. Note the gel which the soft soap forms with the alcohol. Mix half this gel with 100 ml. of 10% sodium chloride solution and warm. What is the solid phase which forms? What is dissolved in the liquid phase? What is the technical term applied to this process? Mix the remainder of the gel with 50 ml. water, stir well, allow to settle, and pour off the supernatant liquid. Divide the liquid into three equal parts. To the first test tube add 10 drops reagent calcium chloride solution. To the second, add 10 drops reagent magnesium chloride solution. To the third, add reagent cone. hydrochloric acid until acidic to litmus. Explain the results and write equations for all reactions, assuming the glyceride to be stearin. Wherein does the commercial manufacture of soap differ in procedure from this method which you have used? What are the principal fatty acids derived from the saponification of the common fats and oils? Write their formulas. Define saponi:fication number. Why does hard water not make a good lather with soap? How does soap soften hard water? What is the action of sodium carbonate in the softening of water? Write equations for (a) the hydrogenation of olein ( b) the elaidinization of oleic acid and ( c) the ozonolysis of elaidic acid. 60.

SURFACE-ACTIVE AGENTS (SURFACTANTS)

(a) Into one beaker put about 200 ml. of tap water. In another beaker put about 200 ml. tap water plus 10 ml. of a 5% solution of "Aerosol O.T." ( dioctyl ester of sodium sulphosuccinate). Take two equal pieces of absorbent cotton from which cottonseed oil has not been removed and crumple each piece until it is about one inch in diameter. Place in each of the liquids and observe at the end of one minute and again at the end of one

47 hour. What is the approximate concentration of the surface-active agent in the liquid used here? ( b) In a test tube place 2 ml. cottonseed oil, 10 ml. water and 3 ml. of a 5% solution of "Gardino!" ( sodium lauryl sulphate). Shake the contents vigorously and observe over a period of about five minutes. Write the structures of these surfactants. What properties of detergents are exhibited in the above experiments? Make a classification of surface-active agents on the basis of structure. Where does soap fit into this classification?

ESTERS 61. PREPARATION OF METHYL SALICYLATE Dissolve 1 g. of salicylic acid in 10 ml. of methanol in a 125 ml. Erlenmeyer. Add 1 ml. cone. sulphuric acid and insert a water condenser in the top of the corked flask. Reflux in a beaker of boiling water for 30 minutes. Pour the contents of the flask into 100 ml. of water. Smell the product. Write the equation for the reaction. Why was sulphuric acid added? What evidence is there that synthetic oil of wintergreen was formed? ·what impurities would you expect to find in the ester resulting? Formulate a reasonable mechanism for the reaction. 0

62. PREPARATION OF IsoAMYL ACETATE (P)

CAUTION! Do not inhale the fumes of acyl halides such as acetyl chloride which are injurious to the mucous membranes. In a 125 ml. Erlenmeyer flask, put 6.0 ml. of isoamyl alcohol ( density = 0.8 g./ml.) and 5.0 ml. acetyl chloride ( density = 1.1 g./ml. ). Allow to stand for two hours and then pour into 50 ml. of 1% sodium hydroxide solution. Observe the fragrance of the ester ( Synthetic Banana Oil). Measure the volume of the crude ester, and calculate the yield of ester. (Density of isoamyl acetate = 0.9 g./ml.) \Vrite the equation for the reaction. Label the crude ester with your name and yield and hand it in. 0

63. PREPARATION oF AcETYL SALICYLIC Acrn ( P)

In a small flask put 2.0 g. salicylic acid, 6.0 ml. acetic anhydride ( density = 1.1 g./ml.) and 3 drops cone. sulphuric acid. Allow to stand for one hour with occasional shaking, then mix with stirring with 50 ml. ice water. Filter by suction. Allow to dry in the air. Weigh and ascertain by the ferric chloride test on a small portion whether or not the sample is free of unchanged salicylic acid. Calculate the yield and hand in the product stating on the label whether its ferric chloride test is positive or negative ( see Exp. 82 ). Represent by general equations, three methods of preparing esters of which the above experiments are examples.

47 hour. What is the approximate concentration of the surface-active agent in the liquid used here? ( b) In a test tube place 2 ml. cottonseed oil, 10 ml. water and 3 ml. of a 5% solution of "Gardino!" ( sodium lauryl sulphate). Shake the contents vigorously and observe over a period of about five minutes. Write the structures of these surfactants. What properties of detergents are exhibited in the above experiments? Make a classification of surface-active agents on the basis of structure. Where does soap fit into this classification?

ESTERS 61. PREPARATION OF METHYL SALICYLATE Dissolve 1 g. of salicylic acid in 10 ml. of methanol in a 125 ml. Erlenmeyer. Add 1 ml. cone. sulphuric acid and insert a water condenser in the top of the corked flask. Reflux in a beaker of boiling water for 30 minutes. Pour the contents of the flask into 100 ml. of water. Smell the product. Write the equation for the reaction. Why was sulphuric acid added? What evidence is there that synthetic oil of wintergreen was formed? ·what impurities would you expect to find in the ester resulting? Formulate a reasonable mechanism for the reaction. 0

62. PREPARATION OF IsoAMYL ACETATE (P)

CAUTION! Do not inhale the fumes of acyl halides such as acetyl chloride which are injurious to the mucous membranes. In a 125 ml. Erlenmeyer flask, put 6.0 ml. of isoamyl alcohol ( density = 0.8 g./ml.) and 5.0 ml. acetyl chloride ( density = 1.1 g./ml. ). Allow to stand for two hours and then pour into 50 ml. of 1% sodium hydroxide solution. Observe the fragrance of the ester ( Synthetic Banana Oil). Measure the volume of the crude ester, and calculate the yield of ester. (Density of isoamyl acetate = 0.9 g./ml.) \Vrite the equation for the reaction. Label the crude ester with your name and yield and hand it in. 0

63. PREPARATION oF AcETYL SALICYLIC Acrn ( P)

In a small flask put 2.0 g. salicylic acid, 6.0 ml. acetic anhydride ( density = 1.1 g./ml.) and 3 drops cone. sulphuric acid. Allow to stand for one hour with occasional shaking, then mix with stirring with 50 ml. ice water. Filter by suction. Allow to dry in the air. Weigh and ascertain by the ferric chloride test on a small portion whether or not the sample is free of unchanged salicylic acid. Calculate the yield and hand in the product stating on the label whether its ferric chloride test is positive or negative ( see Exp. 82 ). Represent by general equations, three methods of preparing esters of which the above experiments are examples.

49 0

64.

ALKALINE HYDROLYSIS ( SAPONIFICATION) OF ETHYL ACETATE

Add 5 ml. of ethyl acetate to 5 ml. of water in a test tube. Note the insolubility of the ester in water. Transfer the mixture to a 250 ml. flask and add 30 ml. of reagent sodium hydroxide solution. Fit the flask with a reflux condenser and heat gently for 20 minutes or until there is but one layer in the flask. Transfer to a small distilling flask and distil off 4 ml. Test the distillate for ethanol by the iodoform test ( Exp. 27). Acidify the solution remaining in the distilling flask with dilute sulphuric acid and again distil about 4 ml. Test this distillate for acidity by Bromothymol Blue indicator. What causes the observed acidity? Write equations for all reactions. Compare these with Experiment 59. Will sulphuric acid be found in this distillate? Explain. For the ammonolysis of an ester, see Experiment 127.

PHENOLS AND ETHERS 65.

RELATIVE Acrn STRENGTHS OF Sol\rn PHENOLS

To separate 3 ml. portions of 5% NaHCOs solution add respectively 3 ml. each of a 5% aqueous-alcoholic solution of (a) phenol, ( b) picric acid, and ( c) 2,4,6-trichlorophenol. Immerse the tubes in a beaker half full of hot water ( about 70°C) and observe at the end of fifteen minutes at which time any reaction will be apparent by the presence of micro bubbles along the walls of the test tube. Evaluate the phenols as to their relative acidities, making use of the rule that "salts of weak acids are decomposed by stronger acids to set free the weak acid." Consult the handbook for the Kion of two of these phenols and see whether your arrangement is in accord with the data cited in respect to these two examples. Write formulas for the phenols listed in this experiment. What explanation is given for the fact that picric acid is more acidic than phenol? 66.

REACTION OF PHENOL WITH BROMINE WATER

To 5 ml. of 1% aqueous phenol solution, add 10 drops of bromine water. Equation? Try the effect of bromine water on 3 ml. benzi=me, and observe how much more readily phenol is brominated. This is known as enhanced activity. Explain why the phenolic group is para and ortho directing and activating. What is the effect of the "Superchlorination" of drinking water on the offensive phenolic impurities present? 0

67.

NITROSATION OF THYMOL

(P)

In a small Erlenmeyer dissolve 1.5 g. thymol in 30 ml. methanol, cool in an ice bath. Add I g. sodium nitrite dissolved in 2 ml. water and then 5 ml. of cone. HCl one ml. per minute with shaking. Allow to stand in the ice bath for 30 minutes with occasional shaking, then at room tern-

49 0

64.

ALKALINE HYDROLYSIS ( SAPONIFICATION) OF ETHYL ACETATE

Add 5 ml. of ethyl acetate to 5 ml. of water in a test tube. Note the insolubility of the ester in water. Transfer the mixture to a 250 ml. flask and add 30 ml. of reagent sodium hydroxide solution. Fit the flask with a reflux condenser and heat gently for 20 minutes or until there is but one layer in the flask. Transfer to a small distilling flask and distil off 4 ml. Test the distillate for ethanol by the iodoform test ( Exp. 27). Acidify the solution remaining in the distilling flask with dilute sulphuric acid and again distil about 4 ml. Test this distillate for acidity by Bromothymol Blue indicator. What causes the observed acidity? Write equations for all reactions. Compare these with Experiment 59. Will sulphuric acid be found in this distillate? Explain. For the ammonolysis of an ester, see Experiment 127.

PHENOLS AND ETHERS 65.

RELATIVE Acrn STRENGTHS OF Sol\rn PHENOLS

To separate 3 ml. portions of 5% NaHCOs solution add respectively 3 ml. each of a 5% aqueous-alcoholic solution of (a) phenol, ( b) picric acid, and ( c) 2,4,6-trichlorophenol. Immerse the tubes in a beaker half full of hot water ( about 70°C) and observe at the end of fifteen minutes at which time any reaction will be apparent by the presence of micro bubbles along the walls of the test tube. Evaluate the phenols as to their relative acidities, making use of the rule that "salts of weak acids are decomposed by stronger acids to set free the weak acid." Consult the handbook for the Kion of two of these phenols and see whether your arrangement is in accord with the data cited in respect to these two examples. Write formulas for the phenols listed in this experiment. What explanation is given for the fact that picric acid is more acidic than phenol? 66.

REACTION OF PHENOL WITH BROMINE WATER

To 5 ml. of 1% aqueous phenol solution, add 10 drops of bromine water. Equation? Try the effect of bromine water on 3 ml. benzi=me, and observe how much more readily phenol is brominated. This is known as enhanced activity. Explain why the phenolic group is para and ortho directing and activating. What is the effect of the "Superchlorination" of drinking water on the offensive phenolic impurities present? 0

67.

NITROSATION OF THYMOL

(P)

In a small Erlenmeyer dissolve 1.5 g. thymol in 30 ml. methanol, cool in an ice bath. Add I g. sodium nitrite dissolved in 2 ml. water and then 5 ml. of cone. HCl one ml. per minute with shaking. Allow to stand in the ice bath for 30 minutes with occasional shaking, then at room tern-

51 perature for 15 minutes. Drown in 150 ml. of ice water, stir well, and allow to stand in the ice bath for a further 5 minutes. Filter off the nitroso compound ( or oxime), wash with 25 ml. cold water, dry in the air, and hand in the sample. Aromatic hydrocarbons will not form nitroso derivatives but phenols will do so easily. Nitroso phenols exist tautomerically with the corresponding quinone monoxime. Illustrate this by an equation. The Liebermann reaction ( Exp. 118) is another example of this reaction. 68. SuscEPTIBILITY OF PHENOLS TO OxrnATION CAUTION! Phenol produces painful wounds. Do not allow it to come in contact with the skin. Wash with ethanol! Place a few crystals of (a) phenol and ( b) quinol in each of two 250 ml. Erlenmeyers, add about 25 ml. water and 25 ml. dilute H2S04 to each. Then carefully pour in about 10 ml. N/10 KMnOc1 solution and observe how quickly and completely the reaction proceeds. Benzoquinone-1,4 is one of the oxidation products of both of these phenols. Write the structure of the products formed. 69. REDUCING ACTION OF AMINOPHENOLS Dilute 5 ml. reagent ammonium hydroxide with 20 ml. water. Prepare some "ammoniacal silver solution" by adding this dilute ammonium hydroxide solution to 5 ml. of 5% silver nitrate solution until the precipitate that first forms just dissolves ( complex ion). To this liquid add a pinch of p-aminophenol, stir well and immerse in a beaker of boiling water for about 5 minutes. Discuss photographic developing in terms of this reaction and give the names and formulas of two organic developers. 70. FORMATION OF QuINHYDRONE (P) Dissolve separately in small Erlenmeyer flasks 1 g. quinol in 15 ml. of warm ( 60° ) ethanol and 1 g. benzoquinone in 20 ml. of warm ethanol. Mix the contents of the two flasks while still warm and stir. Allow to cool and then place on ice for 10 minutes. Filter off the product, air-dry and hand in. Quinhydrone is a redox indicator. ·what type of structure has it? Write its electronic formula. 71. THE INDOPHENOL REACTION To 5 ml. of a dilute solution of phenol, add 5 ml. of a dilute solution of aniline, and 1 ml. of freshly prepared calcium hypochlorite solution ( 0.5 g. in 10 ml. ) . Make half of this liquid acidic and the other half alkaline. Use dilute solutions in order to see the colour. Write the equation for the reaction and note that the oxidation involves some of the hydrogen whose activity has been enhanced. Write reasonable structures for the acid and basic forms of the indicator.

53 72. PREPARA TJON OF PHENOLPHTHALEIN Grind 1 g. phenol and mix well with an equal quantity of powdered phthalic anhydride. Place in a Pyrex test tube, then add 10 drops of concentrated sulphuric acid. Mix well and heat in a Bunsen flame for about 5 minutes or until the melt becomes dark red. Cool. Add carefully 30 ml. of reagent sodium hydroxide solution and stir for a few minutes. Write the equation for the preparation. What is the function of the sulphuric acid? What other product is formed simultaneously by an analogous reaction? To 5 ml. of the above alkaline solution in a beaker add 30 ml of 40% sodium hydroxide solution. Write the equation. To a second 5 ml. portion add cone. HCl to acidity. Equation? What is the chromophoric group in the sodium salt of phenolphthalein? Show that phenolphthalein may be classed as a triphenylmethane derivative. Note also that it is a gamma lactone. 73. PREPARATION OF AN ETHER (METHYL ,8-NAPHTHYL ETHER)-WILLIAMSON SYNTHESIS ( p) Place 4 g. of ,B-naphthol in a 125 ml. Erlenmeyer. Add 10 ml. of methyl alcohol to dissolve the naphthol, then add 2.0 g. of finely crushed potassium hydroxide and 2 ml. of methyl iodide (CAUTION-POISON). Attach the flask to a reflux condenser and boil the contents gently for about 5 minutes. A Granular white precipitate will appear. Distill away about one half of the alcohol from the mixture in the Erlenmeyer, being careful not to overheat. Allow the flask to cool, then add 20 ml. of water and wash the solid thoroughly, breaking any lumps. Decant the wash water into a Buchner funnel. Wash twice more, again pouring the water onto the funnel. Transfer the product to the funnel. Dry by suction, then in the air. Melt a little on a spatula and smell cautiously. Hand in the remainder. Equations. 0

FLUORESCEIN AND ITS DERIVATIVES 74. PREPARATION OF FLUORESCEIN (P) Powder 5 g. of resorcinol, and mix well in an evaporating dish with 4 g. of powdered phthalic anhydride. Transfer to a large test tube. Add 15 drops of concentrated sulphuric acid and heat carefully in a Bunsen flame until the liquid becomes deep red. Hold at this temperature for 2-3 minutes, then quickly pour (GOGGLES!) the melt in a fine stream with vigorous stirring into about 200 ml. of cold water. Dissolve in 25 ml. of reagent sodium hydroxide solution, the portion which will not pour from the test tube. This forms the sodium salt. Save 5 ml. of this solution for Experiment 75. Drown the remainder in a liquid made from 100 ml. dilute sulphuric acid and 150 ml. cold water. Combine the two solid products and filter by suction. Allow the solid to air-dry. When dry save 2.0 g. for Experiment 76 and hand in the remainder. Write the equation for the reaction and show that fluorescein is a triphenylmethane derivative and a gamma lactone.

53 72. PREPARA TJON OF PHENOLPHTHALEIN Grind 1 g. phenol and mix well with an equal quantity of powdered phthalic anhydride. Place in a Pyrex test tube, then add 10 drops of concentrated sulphuric acid. Mix well and heat in a Bunsen flame for about 5 minutes or until the melt becomes dark red. Cool. Add carefully 30 ml. of reagent sodium hydroxide solution and stir for a few minutes. Write the equation for the preparation. What is the function of the sulphuric acid? What other product is formed simultaneously by an analogous reaction? To 5 ml. of the above alkaline solution in a beaker add 30 ml of 40% sodium hydroxide solution. Write the equation. To a second 5 ml. portion add cone. HCl to acidity. Equation? What is the chromophoric group in the sodium salt of phenolphthalein? Show that phenolphthalein may be classed as a triphenylmethane derivative. Note also that it is a gamma lactone. 73. PREPARATION OF AN ETHER (METHYL ,8-NAPHTHYL ETHER)-WILLIAMSON SYNTHESIS ( p) Place 4 g. of ,B-naphthol in a 125 ml. Erlenmeyer. Add 10 ml. of methyl alcohol to dissolve the naphthol, then add 2.0 g. of finely crushed potassium hydroxide and 2 ml. of methyl iodide (CAUTION-POISON). Attach the flask to a reflux condenser and boil the contents gently for about 5 minutes. A Granular white precipitate will appear. Distill away about one half of the alcohol from the mixture in the Erlenmeyer, being careful not to overheat. Allow the flask to cool, then add 20 ml. of water and wash the solid thoroughly, breaking any lumps. Decant the wash water into a Buchner funnel. Wash twice more, again pouring the water onto the funnel. Transfer the product to the funnel. Dry by suction, then in the air. Melt a little on a spatula and smell cautiously. Hand in the remainder. Equations. 0

FLUORESCEIN AND ITS DERIVATIVES 74. PREPARATION OF FLUORESCEIN (P) Powder 5 g. of resorcinol, and mix well in an evaporating dish with 4 g. of powdered phthalic anhydride. Transfer to a large test tube. Add 15 drops of concentrated sulphuric acid and heat carefully in a Bunsen flame until the liquid becomes deep red. Hold at this temperature for 2-3 minutes, then quickly pour (GOGGLES!) the melt in a fine stream with vigorous stirring into about 200 ml. of cold water. Dissolve in 25 ml. of reagent sodium hydroxide solution, the portion which will not pour from the test tube. This forms the sodium salt. Save 5 ml. of this solution for Experiment 75. Drown the remainder in a liquid made from 100 ml. dilute sulphuric acid and 150 ml. cold water. Combine the two solid products and filter by suction. Allow the solid to air-dry. When dry save 2.0 g. for Experiment 76 and hand in the remainder. Write the equation for the reaction and show that fluorescein is a triphenylmethane derivative and a gamma lactone.

55 75. FLUORESCENCE OF THE SODIUM SALT OF FLUORESCEIN Take the 5 ml. of solution of sodium salt of fluorescein ( Exp. 74) and dilute to three times its volume with water. Observe the appearance by (a) transmitted and ( b) reflected light. Examine the approximate degree of dilution which can be attained before the fluorescence ceases to be perceptible. The structure found in salts of fluorane and fluorescein involves a pyrane ring fused to a para quinonoid ring and is common to many phthaleines, sulphonphthaleines and the commercial dyes, the Rhodamines. Substances whose formulas contain this structure fluoresce. Draw an outline of this structure and label the various portions. Write a note comparing fluorescence, luminescence and phosphorescence. ( See an Encyclopaedia. ) 76. BROMINATION OF FLUORESCEIN ( p) The enhanced activity imparted by the free phenolic groups in fluorescein to the ortho hydrogen atoms makes possible a very easy substitution of these hydrogen atoms by bromine. CAUTION! Liquid bromine causes painful and deep burns which are slow to heal. If any gets on the skin, apply glycerol immediately. Do not wash with water! In a 125 ml. Erlenmeyer, dissolve 2.0 g. dry powdered fluorescein ( Exp. 74) in 25 ml. ethanol. In the fume hood carefully add gradually and with shaking, 2 ml. of bromine ( density = 3.1 g./ml.). This addition should take a couple of minutes. Allow to stand for about 10 minutes. Add with stirring 150 ml. ice water and allow to stand for several minutes in an ice bath. Filter and wash with three portions of 10 ml. cold water. Write the equation for the reaction. Keep out approximately two-thirds of the moist filter cake for subsequent experiments. Air-dry and hand in the remainder. 0

77. FORMATION OF EosIN Eosin, the sodium salt of tetrabromofluorescein, can be prepared as follows. Dissolve about ¼ of the moist tetrabromo compound ( Exp. 76) in 25 ml. of 2% NaOH solution which will give an aqueous solution of eosin. Observe this solution by transmitted and by reflected light and note the fluorescence exhibited. Write the equation for the reaction.

78. PREPARATION OF THE AMMONIUM SALT OF TETRABROMOFLUORESCEIN (P) ( CAUTION! FUME HOOD!) Dissolve the remainder of the moist tetrabromo compound ( Exp. 76) in 10 ml. cone. 28% ammonium hydroxide. Stir for a few minutes. Note the vivid fluorescence. Put the coloured solution into an evaporating dish and place the dish on a filter paper labelled with your name, in one of the wooden trays provided, where it will be set away to evaporate until next laboratory period. When dry, observe the greenish-red iridescence of the ammonium salt. Write the equation for the reaction. Note the ready solubility of a pinch of the salt in water.

57 Indicate the similarity of structure in Eosin and Mercurochrome, designating the structural portion responsible for the fluorescence. Note the depth of reddish-orange produced in the above bromination of fluorescein. Compare structurally Eosin Bluish and Eosin Yellowish ( see Merck's Index) and note how nitration shifts the shade into the green. Note the formula for Erythrosine (Merck's Index), a colour permitted in the colouring of foods and also useful in the sensitizing of silver halide emulsions (photographic). Show by its structure that it is a phthalein. Fluorescent lacquers are now being manufactured by incorporating an organic fluorescent dye with an inorganic luminous pigment in a suitable vehicle. View the card at the front of the room and spread a small amount of each lacquer on a portion of a sheet of your notebook. Examine the card submitted, showing the effect of substitution bromination on the shade of a dye.

ENOLS AND QUINONES 79.

ENOLIC ACIDI'IT OF ACETONE

To 5 ml. of acetone add a clean piece of sodium. The white precipitate obtained is the sodium enolate of acetone. Dilute with 10 cc. water and test with litmus. Write the structure for acetone which is consistent with this result, and then, the equation for the reaction. 80.

FORMATION OF THE CUPruc ENoLATE OF AcETOACETIC EsTER

To 8 ml. cone. cupric acetate solution add 2 ml. acetoacetic ester and stir. Allow to stand for about 10 minutes, then filter and observe the colour of the enolate. Write the structure attributed to the enolate. What type of structure is this, and why is it so named? 81.

AcTION OF BROMINE ON AcETOACETIC ESTER

To 2 ml. acetoacetic ester add 10 drops of 5% bromine in carbon tetrachloride. Shake the resulting liquid. Explain the result and write an equation for the reaction. 82.

THE FERRIC CHLORIDE REACTION OF ENOLS AND PHENOLS

Add 5 drops ferric chloride solution to 5 ml. portions of acetone, of dilute aqueous solutions of phenol, quinol, resorcinol, beta naphthol, p-nitrophenol, o-nitrophenol, vanillin and salicylic acid and dilute aqueous-alcoholic solutions of acetyl acetone ( diacetone), acetoacetic ester, phenylacetaldehyde and benzoyl acetone. Tabulate the results, write formulas for the above substances and represent any tautomerism indicated. Which of the above substances appear to be the least enolized under the existing conditions? Do you notice any notable difference in shade produced with phenols and with enols? This colour reaction is probably due to complex ions in which hexacovalent iron is bonded with the phenolic or enolic structure as the case may be to give co-ordination complexes.

57 Indicate the similarity of structure in Eosin and Mercurochrome, designating the structural portion responsible for the fluorescence. Note the depth of reddish-orange produced in the above bromination of fluorescein. Compare structurally Eosin Bluish and Eosin Yellowish ( see Merck's Index) and note how nitration shifts the shade into the green. Note the formula for Erythrosine (Merck's Index), a colour permitted in the colouring of foods and also useful in the sensitizing of silver halide emulsions (photographic). Show by its structure that it is a phthalein. Fluorescent lacquers are now being manufactured by incorporating an organic fluorescent dye with an inorganic luminous pigment in a suitable vehicle. View the card at the front of the room and spread a small amount of each lacquer on a portion of a sheet of your notebook. Examine the card submitted, showing the effect of substitution bromination on the shade of a dye.

ENOLS AND QUINONES 79.

ENOLIC ACIDI'IT OF ACETONE

To 5 ml. of acetone add a clean piece of sodium. The white precipitate obtained is the sodium enolate of acetone. Dilute with 10 cc. water and test with litmus. Write the structure for acetone which is consistent with this result, and then, the equation for the reaction. 80.

FORMATION OF THE CUPruc ENoLATE OF AcETOACETIC EsTER

To 8 ml. cone. cupric acetate solution add 2 ml. acetoacetic ester and stir. Allow to stand for about 10 minutes, then filter and observe the colour of the enolate. Write the structure attributed to the enolate. What type of structure is this, and why is it so named? 81.

AcTION OF BROMINE ON AcETOACETIC ESTER

To 2 ml. acetoacetic ester add 10 drops of 5% bromine in carbon tetrachloride. Shake the resulting liquid. Explain the result and write an equation for the reaction. 82.

THE FERRIC CHLORIDE REACTION OF ENOLS AND PHENOLS

Add 5 drops ferric chloride solution to 5 ml. portions of acetone, of dilute aqueous solutions of phenol, quinol, resorcinol, beta naphthol, p-nitrophenol, o-nitrophenol, vanillin and salicylic acid and dilute aqueous-alcoholic solutions of acetyl acetone ( diacetone), acetoacetic ester, phenylacetaldehyde and benzoyl acetone. Tabulate the results, write formulas for the above substances and represent any tautomerism indicated. Which of the above substances appear to be the least enolized under the existing conditions? Do you notice any notable difference in shade produced with phenols and with enols? This colour reaction is probably due to complex ions in which hexacovalent iron is bonded with the phenolic or enolic structure as the case may be to give co-ordination complexes.

59 A few phenols fail to give this colour reaction, the most important of which are naphthols, ortho-nitro-phenol, and meta and para phenolic acids. ( To what class of phenolic acids does salicylic belong?) 83. FORMATION OF THE POTASSIUM DIENOLATE OF BENZOIN

Boil a pinch of benzoin with 5 ml. Fehling's solution. Equation? This reaction is general for alpha-hydroxy ketones and is important in carbohydrate chemistry. In a 50 ml. Erlenmeyer, put 10 ml. ethanol and about 0.1 g. each of benzoin and benzil. Add 5 drops 10% alcoholic potassium hydroxide solution, allow to stand for a minute and then shake vigorously so that air will be mixed with the liquid. Repeat the operation of adding alcoholic KOH and shaking with air as long as the colour can be made to appear and to disappear again. The potassium dienolate of stilbendiol or isostilbendiol is formed, and can, if desired, be isolated as yellow crystals. The reddishpurple solution which is sensitive to the oxygen of the air and is decolorized thereby, is probably due to a free radical of para quinonoid structure. On auto-oxidation, this free radical is converted partly into benzil and partly into potassium benzoate. Write the equations for the reaction and account structurally for the colour and its disappearance on shaking with air. \Vrite the formulas for stilbene, isostilbene and stilboestrol in such a manner as to indicate their common structural portion. 84. ALKALINE REDUCTION (VATTING) OF ANTHRAQUINONE

Into one test tube put 5 ml. reagent sodium hydroxide solution and sufficient zinc dust to cover the bottom of the test tube. Into a second test tube put 5 ml. reagent sodium hydroxide and sufficient sodium hydrosulphite to cover the bottom of the tube. Add a pinch of anthraquinone to each tube and heat carefully. The colour is due to the formation of the sodium salt of anthrahydroquinone ( anthraquinol). Anthrahydroquinone and oxanthrone are tautomers. Write the equilibrium expression and show the relationship between the respective sodium salts. This salt is soluble in water and it is in this way that dyes of the indigoid or anthraquinonoid type are applied to a fibre. Show that the red colour can be caused to disappear by shaking the solution with air, which oxidizes the red salt to anthraquinone. Write equations for the reactions. Up until recently the Chinese vatted Indigo Blue with soda and glucose. What reaction would likely result here? List the formulas, names and colours of the anthraquinone dyes submitted for inspection, and note how a change in position of a substituent auxochrome will alter the shade of the dye. What are the structural requirements for enolization? Give formulas for two auxochrome groups. 0

85. PREPARATION OF 1,4-NAPHTHOQUINONE (P)

Dissolve 7.0 g. of chromic anhydride ( CrOs) in 35 ml. of ice cold 80% acetic acid in a 250 ml. beaker. CAUTION: avoid contact with chromic

61 anhydride as it causes severe bums. To this slowly add with vigorous stirring, over a period of 5 minutes, a cold solution of 4.0 g. of naphthalene in 50 ml. of glacial acetic acid. Keeping the liquid in ice for the first hour, stir occasionally for the remainder of the period and allow to stand until the next laboratory period. Pour with vigorous stirring into 500 ml. of ice water. Allow to stand for one hour. Rinse out the beaker with 25 ml. dilute acetic acid and add this to the drowned mass. Filter off the precipitate, wash acidfree with cold water, air-dry, and hand in. Write the equation for the reaction. To what is the colour of the product due? Give the formulas and names for the isomeric naphthoquinones and for synthetic Vitamin K. Polynuclear aromatic hydrocarbons generally oxidize in the manner illustrated by this experiment. 86. A CHAIN REACTION-THE BROMINATION OF 2,6-DIBENZALCYCLOHEXANONE In a clean, dry test tube, place sufficient purified dibenzalcyclohexanone to cover the curved part. Dissolve it in 3 ml. carbon tetrachloride by heating it. Thoroughly cool the solution in running water, and then, keeping the system cooled, add from a dropping tube 8 drops of a 5% solution of bromine in carbon tetrachloride. Shake for a few minutes, note any change, and explain the results. Then add 2 drops of 2% hydrogen peroxide solution in 50% methanol-water and another 8 drops of the bromine solution. After one minute, add a trace of diphenylamine. Then add further portions of bromine solution as long as it is being decolorized. Finally, transfer to an evaporating dish. Allow the liquid to evaporate on a water-bath in order to observe the colour of the products. Explain the results, and by means of equations account for all colour changes noticed.

HIGH POLYMERS-RESINS AND PLASTICS 87. CONDENSATION POLYMERIZATION OF BENZYL ALCOHOL (P) In a small Erlenmeyer flask place 25 ml. of concentrated sulphuric acid. Then add carefully, with brisk stirring (GOGGLES!!), 3.0 ml. of benzyl alcohol ( density = 1.04 g./ml.). Cool the resulting system in running water, stirring to break up any lumps, and allow to stand at room temperature for about ten minutes. Then drown with vigorous stirring in about 300 ml. water. Break up any lumps as well as possible, filter by suction and wash acid-free with water. Dry and weigh the polymeric hydrocarbon. Write a portion of the structure assigned to it. Hand in the product.

88. FORMATION OF A GLYPTAL RESIN (P) In a crucible on an asbestos mat, over a low flame, heat a mixture of 3 g. powdered phthalic anhydride and 1 ml. glycerol plus a pinch of anhydrous sodium acetate. Stir occasionally and heat gently as long as water vapour is being evolved ( about ½ hour). Then, without charring, quickly raise the

61 anhydride as it causes severe bums. To this slowly add with vigorous stirring, over a period of 5 minutes, a cold solution of 4.0 g. of naphthalene in 50 ml. of glacial acetic acid. Keeping the liquid in ice for the first hour, stir occasionally for the remainder of the period and allow to stand until the next laboratory period. Pour with vigorous stirring into 500 ml. of ice water. Allow to stand for one hour. Rinse out the beaker with 25 ml. dilute acetic acid and add this to the drowned mass. Filter off the precipitate, wash acidfree with cold water, air-dry, and hand in. Write the equation for the reaction. To what is the colour of the product due? Give the formulas and names for the isomeric naphthoquinones and for synthetic Vitamin K. Polynuclear aromatic hydrocarbons generally oxidize in the manner illustrated by this experiment. 86. A CHAIN REACTION-THE BROMINATION OF 2,6-DIBENZALCYCLOHEXANONE In a clean, dry test tube, place sufficient purified dibenzalcyclohexanone to cover the curved part. Dissolve it in 3 ml. carbon tetrachloride by heating it. Thoroughly cool the solution in running water, and then, keeping the system cooled, add from a dropping tube 8 drops of a 5% solution of bromine in carbon tetrachloride. Shake for a few minutes, note any change, and explain the results. Then add 2 drops of 2% hydrogen peroxide solution in 50% methanol-water and another 8 drops of the bromine solution. After one minute, add a trace of diphenylamine. Then add further portions of bromine solution as long as it is being decolorized. Finally, transfer to an evaporating dish. Allow the liquid to evaporate on a water-bath in order to observe the colour of the products. Explain the results, and by means of equations account for all colour changes noticed.

HIGH POLYMERS-RESINS AND PLASTICS 87. CONDENSATION POLYMERIZATION OF BENZYL ALCOHOL (P) In a small Erlenmeyer flask place 25 ml. of concentrated sulphuric acid. Then add carefully, with brisk stirring (GOGGLES!!), 3.0 ml. of benzyl alcohol ( density = 1.04 g./ml.). Cool the resulting system in running water, stirring to break up any lumps, and allow to stand at room temperature for about ten minutes. Then drown with vigorous stirring in about 300 ml. water. Break up any lumps as well as possible, filter by suction and wash acid-free with water. Dry and weigh the polymeric hydrocarbon. Write a portion of the structure assigned to it. Hand in the product.

88. FORMATION OF A GLYPTAL RESIN (P) In a crucible on an asbestos mat, over a low flame, heat a mixture of 3 g. powdered phthalic anhydride and 1 ml. glycerol plus a pinch of anhydrous sodium acetate. Stir occasionally and heat gently as long as water vapour is being evolved ( about ½ hour). Then, without charring, quickly raise the

63 temperature of the system until large bubbles form and the liquid puffs up into a voluminous sticky mass. Allow to cool and powder the polymer. Write a portion of the structure attributed to it. Hand in the product. What structural characteristics are thought to be involved when the product passes from a thermoplastic to a thermosetting resin? 89.

PREPARATION OF A PHENOL RESIN

Take 1 gram of hexamethylenetetramine made in a previous experiment ( Exp. 44), and mix thoroughly with an equal amount of phenol. Heat evenly and gently in a crucible over a low flame, being careful not to char. Allow to cool. Result? Can the product be made plastic again on heating? This is the procedure for making the Bakelite type of resin. It consists in causing certain aldehydes and phenols to react in the presence of mild alkalis. Write a portion of the structure attributed to this resin. 90.

PREPARATION OF CELLULOSE ACETATE

(P)

In a small flask, place 15 ml. of glacial ( 100%) acetic acid, 10 ml. of acetic anhydride, 10 drops of concentrated sulphuric acid and two 10 cm. filter papers, torn into small pieces. Stir, so that most of the air bubbles are removed. Stopper the flask with a cork and let stand until the next laboratory period. Then pour the liquid in a thin stream, and with stirring, into about 300 ml. of cold water. Filter the resulting slurry through a towel and squeeze out as much liquid as possible, wash free of acid, set aside in a warm place to dry. When dry, put about one-third of the product in a test tube, and add about 10 ml. chloroform. Cork and allow to stand with occasional shaking. When solution has been effected, pour some onto a clean watch glass and allow to evaporate slowly. When dry, lift the edges of the film, and remove it slowly from the glass. Will it ignite readily? A modification of this procedure is used in the manufacture of motion picture film. What are its advantages over films made from the lower nitrates of cellulose? Celanese, an artificial fibre, and Tenite, a cellulose acetate plastic, are similarly made. The latter is a thermoplastic resin and is used in injection moulding of combs, ornaments, costume jewelry, radio and television parts, etc. Hand in the remainder of the crude product. Write a portion of the structure attributed to cellulose and indicate the esterification to the acetate. 91.

DEPOLYMERIZATION OF LUCITE

Place 5 g. methyl methacrylate polymer (Lucite) in a small ( 50 ml. ) distilling flask and attach to a water-condenser in which no water is circulating. Use a test tube surrounded by water as a receiver. The inside of the condenser tube must be DRY. Heat with a small luminous flame ( no asbestos mat!), keeping the flame constantly moving around the bottom

65 half of the flask. At about 300° the polymer will soften and undergo rapid depolymerization into the monomer which will distil over. Avoid local overheating! Continue the distillation with a larger flame until the drops of distillate become yellow (charring). Depolymerization by heat is a common property of addition polymers. ( Compare paraformaldehyde-Exp. 43.) 92. POLYMERIZATION OF METHYL METHACRYLATE ( p)

CAUTION! Benzoyl peroxide is a very dangerous explosive and should not be brought near any warm object or touched with anything which is warm. Great care must be exercised when working with it! To the monomer obtained in the previous experiment, add a very small amount ( just sufficient to cover the end of a knife blade) of benzoyl peroxide, shake, stopper the tube loosely and heat in a boiling water-bath for ten minutes. Allow to stand until the next laboratory period. Hand in the test tube containing this polymer. Write a suitable structure for a portion of the Lucite molecule. Make a classification of 10 diversified plastics and elastomers from the standpoint of structure, indicating the type, recurring structural unit, and common trade names. List six common chemicals which are the starting point for the synthesis of high polymers. 93. PREPARATION OF A PoLYSULPIIlDE RUBBER-TIIlOKOL

TYPE

(P)

Dissolve 2 g. of sodium hydroxide in 50 ml. of water contained in a 250 ml. beaker. Heat this solution to boiling, add 4 g. of powdered sulphur and stir until all the sulphur has dissolved. As the polysulphide is formed, the solution turns from light yellow to dark brown. Cool the solution to 70° and add 10 ml. of ethylene dichloride ( density = 1.26 g./ml. ). Stir the mixture vigorously so that the ethylene dichloride is suspended in the polysulphide mixture. The "synthetic" rubber slowly forms at the junction between the two liquids and collects a spongy lump at the bottom of the beaker as stirring is continued. After the reaction has been completed, remove the white-to-yellow rubber-like material from the solution, and wash thoroughly. Dry the polymer and hand in a portion of it.

MOLECULAR REARRANGEMENT 94. PINACOL-PINACOLONE REARRANGEMENT ( p)

Into a 250 ml. Erlenmeyer pour 20 ml. reagent dilute H2SO4. Dissolve the pinacol or pinacol hydrate previously prepared ( Exp. 50) in this dilute acid. Attach a reflux condenser and boil for about 5 minutes observing any changes which take place. Cool until the boiling ceases, transfer to a 50 ml. distilling flask and distil off about one-third of the liquid. Pour this distillate into a test tube, stopper well, saturate the aqueous layer with salt and cool well in ice allowing to stand for about½ hour. Smell the upper

65 half of the flask. At about 300° the polymer will soften and undergo rapid depolymerization into the monomer which will distil over. Avoid local overheating! Continue the distillation with a larger flame until the drops of distillate become yellow (charring). Depolymerization by heat is a common property of addition polymers. ( Compare paraformaldehyde-Exp. 43.) 92. POLYMERIZATION OF METHYL METHACRYLATE ( p)

CAUTION! Benzoyl peroxide is a very dangerous explosive and should not be brought near any warm object or touched with anything which is warm. Great care must be exercised when working with it! To the monomer obtained in the previous experiment, add a very small amount ( just sufficient to cover the end of a knife blade) of benzoyl peroxide, shake, stopper the tube loosely and heat in a boiling water-bath for ten minutes. Allow to stand until the next laboratory period. Hand in the test tube containing this polymer. Write a suitable structure for a portion of the Lucite molecule. Make a classification of 10 diversified plastics and elastomers from the standpoint of structure, indicating the type, recurring structural unit, and common trade names. List six common chemicals which are the starting point for the synthesis of high polymers. 93. PREPARATION OF A PoLYSULPIIlDE RUBBER-TIIlOKOL

TYPE

(P)

Dissolve 2 g. of sodium hydroxide in 50 ml. of water contained in a 250 ml. beaker. Heat this solution to boiling, add 4 g. of powdered sulphur and stir until all the sulphur has dissolved. As the polysulphide is formed, the solution turns from light yellow to dark brown. Cool the solution to 70° and add 10 ml. of ethylene dichloride ( density = 1.26 g./ml. ). Stir the mixture vigorously so that the ethylene dichloride is suspended in the polysulphide mixture. The "synthetic" rubber slowly forms at the junction between the two liquids and collects a spongy lump at the bottom of the beaker as stirring is continued. After the reaction has been completed, remove the white-to-yellow rubber-like material from the solution, and wash thoroughly. Dry the polymer and hand in a portion of it.

MOLECULAR REARRANGEMENT 94. PINACOL-PINACOLONE REARRANGEMENT ( p)

Into a 250 ml. Erlenmeyer pour 20 ml. reagent dilute H2SO4. Dissolve the pinacol or pinacol hydrate previously prepared ( Exp. 50) in this dilute acid. Attach a reflux condenser and boil for about 5 minutes observing any changes which take place. Cool until the boiling ceases, transfer to a 50 ml. distilling flask and distil off about one-third of the liquid. Pour this distillate into a test tube, stopper well, saturate the aqueous layer with salt and cool well in ice allowing to stand for about½ hour. Smell the upper

67 layer which is crude pinacolone, and note whether its odour is comparable to that of camphor. Hand in the product without attempting to separate it from the aqueous phase. Compare the structures of pinacolone and camphor in such a wa:v as to indicate common structural portions. Write structures and names for the secondary alcohols which should result from the reduction of camphor and of pinacolone. Account for the optical activity of natural camphor. What will be the oxidation products of pinacolone? Make a tabulation of some of the important terpene derivatives and classify them according to structure.

CARBOHYDRATES 95.

CARBONIZATION OF CARBOHYDRATES

In a crucible place sufficient glucose or sucrose to cover the bottom well. Add 1 ml. cone. H2S04, observe at room temperature for a few minutes, then warm cautiously for a few minutes. Discuss the reactions taking place and comment upon the appropriateness of the term "carbohydrate." 96.

MouscH's TEST FOR CARBOHYDRATES

Dilute 1 ml. of each of the following 20% sugar solutions: sucrose, maltose, lactose, glucose, fructose, to 5 ml. with water, add 10 drops Molisch's reagent, shake, and introduce carefully over 3 ml. of concentrated sulphuric acid in a test tube, by holding the latter in an inclined position. This test indicates the presence of a carbohydrate portion in a compound.

97.

REACTIONS OF REDUCING SUGARS WITH MILD OXIDIZERS

(a) Benedict's Test Boil 5 ml. of Benedict's reagent alone; it should remain clear. Then into each of five labelled test tubes, put 5 ml. of Benedict's solution, and add 10 drops of the various sugar solutions provided ( Exp. 96) respectively to the test tubes. Place in a beaker of boiling water, and observe after five minutes. Write the equations for the reaction between Benedict's reagent and glucose assuming the active part of the former to be the cupric alcoholate of sodium citrate.

( b) Nylander's Test Nylander's solution is a solution of bismuth hydroxide in concentrated sodium hydroxide forming sodium bismuthate. It is used in the same manner as Benedict's and reducing sugars reduce it to metallic bismuth which comes down as a fine black precipitate. Using the same procedure as in (a) test the five sugar solutions with it.

67 layer which is crude pinacolone, and note whether its odour is comparable to that of camphor. Hand in the product without attempting to separate it from the aqueous phase. Compare the structures of pinacolone and camphor in such a wa:v as to indicate common structural portions. Write structures and names for the secondary alcohols which should result from the reduction of camphor and of pinacolone. Account for the optical activity of natural camphor. What will be the oxidation products of pinacolone? Make a tabulation of some of the important terpene derivatives and classify them according to structure.

CARBOHYDRATES 95.

CARBONIZATION OF CARBOHYDRATES

In a crucible place sufficient glucose or sucrose to cover the bottom well. Add 1 ml. cone. H2S04, observe at room temperature for a few minutes, then warm cautiously for a few minutes. Discuss the reactions taking place and comment upon the appropriateness of the term "carbohydrate." 96.

MouscH's TEST FOR CARBOHYDRATES

Dilute 1 ml. of each of the following 20% sugar solutions: sucrose, maltose, lactose, glucose, fructose, to 5 ml. with water, add 10 drops Molisch's reagent, shake, and introduce carefully over 3 ml. of concentrated sulphuric acid in a test tube, by holding the latter in an inclined position. This test indicates the presence of a carbohydrate portion in a compound.

97.

REACTIONS OF REDUCING SUGARS WITH MILD OXIDIZERS

(a) Benedict's Test Boil 5 ml. of Benedict's reagent alone; it should remain clear. Then into each of five labelled test tubes, put 5 ml. of Benedict's solution, and add 10 drops of the various sugar solutions provided ( Exp. 96) respectively to the test tubes. Place in a beaker of boiling water, and observe after five minutes. Write the equations for the reaction between Benedict's reagent and glucose assuming the active part of the former to be the cupric alcoholate of sodium citrate.

( b) Nylander's Test Nylander's solution is a solution of bismuth hydroxide in concentrated sodium hydroxide forming sodium bismuthate. It is used in the same manner as Benedict's and reducing sugars reduce it to metallic bismuth which comes down as a fine black precipitate. Using the same procedure as in (a) test the five sugar solutions with it.

69 Write the equation for the reaction between glucose and Nylander's solution. ( c) Tollens' Test-Formation of Silver Mirror Clean the inside of a test tube by boiling some reagent sodium hydroxide to dissolve out all grease. Then rinse the tube out well, and place in it about 10 ml. of Tollens' ammoniacal silver solution and add 2 drops reagent sodium hydroxide solution. To this add 20 drops glucose solution, shake, then immerse in half a beaker of boiling water. Any reducing sugar will give a silver mirror in this manner, but glucose is most frequently used. Write an equation for this reaction. N.B.-Carbohydrates giving positive tests in Experiments 97 (a), ( b), ( c) are termed "REDUCING SuGARs." 98. ESTERIFICATION OF D-GLUCOPYRANOSE BY BENZOYL CHLORIDE ( p) In a 125 ml. stoppered Erlenmeyer, dissolve 2.0 g. dextrose in 25 ml. of reagent sodium hydroxide solution and then in a fume hood add 3.0 ml. of benzoyl chloride. (N.B.-Benzoyl chloride is a powerful lachrymator!) Shake vigorously until the odour of benzoyl chloride has disappeared. Then drown in 250 ml. dilute hydrochloric acid, filter off the glucose pentabenzoate, wash twice with 15 ml. portions of cold water, dry in the air, and hand in. Write equation. What type of reaction is the above? 99. FORMATION OF OSAZONES Into three test tubes, place respectively 1 ml. of freshly prepared 20% solutions of glucose, maltose and lactose. Dilute each to 10 ml. with water, and to each add 3 ml. 10% phenylhydrazine hydrochloride solution and sufficient anhydrous sodium acetate to cover a twenty-five cent piece. Place in a beaker of boiling water and observe the comparative rates of appearance of the yellow crystals of the osazones, recording the order in which they appear. If they do not form in the heated solution within 5 minutes, cool it. Make a drawing of each type of crystalline osazone as viewed under the microscope. Write the equation for the formation of glucosazone. Write a tautomeric structure for the product which would account for the fact that it is coloured. Indicate why D-glucose and D-fructose should give the same osazone. 100. HYDROLYSIS OF A DISACCHARIDE ( SUCROSE) To about 5 ml. of cane sugar solution add about 3 drops of concentrated hydrochloric acid and boil for a few minutes. Cool, make alkaline with sodium hydroxide and test with 5 ml. boiling Benedict's solution. Write the equation for the hydrolysis of cane sugar using structural formulas. What monosaccharides are produced? Why is this process termed "inversion"? Make a labelled diagram of a polarimeter and show how the progress of the inversion could be observed with it.

71 101. HYDROLYSIS OF A PoLYSACCHARIDE (STARCH)

(a) By Acids Test 2 ml. starch suspension with 5 ml. boiling Benedict's solution. Heat 5 ml. of the starch paste with 1 ml. of dilute hydrochloric acid and at the end of every half minute, withdraw a drop on a stirring rod, and touch it to a drop of very dilute iodine solution ( 0.01%) on a spot plate. Note the different shades of red imparted to the iodine as the starch passes through the dextrin stages. When the product becomes a clear solution, neutralize it, and test with an equal quantity of hot Benedict's solution. Indicate some of the recognizable stages in the hydrolysis of starch. What is the monosaccharide formed by its degradation? Why is this an important chemical reaction from the standpoint of nutrition? How is corn syrup made? What is amylose and of what importance? ( b) By Saliva To 5 ml. of starch suspension, add about 2 ml. of fresh saliva and immerse in a beaker of warm water for about ten minutes. Then test separate portions for the presence of (a) starch and ( b) reducing sugars. What is the enzyme in saliva which is responsible for this change? List the main constituents of flour and some of the ingredients added to a cake mix. 102. PREPARATION OF CELLULOSE HEXANITRATE ( GuNCOTTON) GoGGLEs! Into a beaker carefully pour 15 ml. of concentrated sulphuric acid into 15 ml. concentrated nitric acid. To this liquid, after cooling for several minutes, add about 1 g. absorbent cotton, and stir occasionally. After about seven minutes, withdraw the nitrated cotton, and remove most of the acid by pressing it with a glass rod against the side of the beaker. Transfer the nitrated cotton to a beaker containing 300 ml. cold water, wash until neutral in running water (litmus), squeezing out from time to time. Pull out and set aside to dry in the air until next day. When dry, CAREFULLY ignite it on your asbestos mat by means of your gas lighter. Why is the product called "hexanitrate"? Show that there is sufficient oxygen content in the molecule to completely burn the carbon and hydrogen content. What are some of the products of combustion of cellulose hexanitrate? How is cordite made? What is a propellant? How does it differ from a high explosive? List four examples of the latter with formulas. What are some uses of the lower nitrates of cellulose? List five "high energy" chemicals used in rockets.

•10s.

PREPARATION oF CELLuLosE XANTHATE (VIscosE)

In a beaker add two filter papers, torn in shreds, to 15 ml. of cold 18% sodium hydroxide solution, and stir thoroughly. Cover the beaker and allow to stand for two hours. Then express as much of the sodium hydroxide as possible from the pulp, and place the pulp or "alkalicellulose" loosely in

73 a corked Erlenmeyer. Add 10 ml. of carbon disulphide ( KEEP FLAMES AwAY) and stopper tightly. Put away to "age" until the next laboratory period. Note any change in colour. Pour off any unchanged carbon disulphide, then add 10 ml. of a 3% solution of sodium hydroxide and allow to stand for one hour, stirring occasionally. Add 5 ml. of water and stir until a smooth uniform product results. This is the viscose solution. Squirt some of the viscose solution into about 200 ml. of dilute sulphuric acid and note the regeneration of cellulose hydrate. This is the basis of the manufacture of viscose rayon, cellophane, cellulose sponges, cellulose sausage casings, etc. 104. HYDROLYSIS OF CELLULOSE

Grind a 10 cm. filter paper carefully with about 1 ml. concentrated sulphuric acid in a mortar until a sticky mass is obtained. CAUTIOUSLY add 5 ml. water, transfer to a test tube, and boil the resulting liquid for about two minutes. Neutralize the solution with reagent sodium hydroxide and test for a reducing sugar with 5 ml. boiling Benedict's solution. Indicate some of the recognizable stages in the hydrolysis of cellulose. Write a portion of the structure attributed to cellulose and indicate the recurring cellobiose unit therein. List three plentiful natural sources of cellulose, give the approximate percentage of cellulose in each, and indicate some of the impurities present. 105. OXIDATION OF LACTOSE (P) Lactose on oxidation with nitric acid forms the two dibasic sugar-acids, mucic and D-saccharic, as well as decomposition products, e.g. oxalic acid. In a beaker on a water bath, heat 8 g. lactose with 75 ml. dilute reagent nitric acid, keeping the system at 70°-80° until the evolution of oxides of nitrogen has ceased ( FUME HOOD). Evaporate to half volume on an asbestos mat. Allow to cool until next laboratory period. Filter off the mucic acid, wash once with 10 cc. methanol, dry, and hand in. Allow the filtrate to evaporate at room temperature in an evaporating dish and note whether oxalic acid and D-saccharic acid crystallize out. Write the formula for lactose and indicate from what portions of the structure the above mentioned three acids were probably derived. Why does mucic acid bear no D- or L-designation? Save the mucic acid for a subsequent experiment ( Exp. 134) when it is returned to you. 106. REDUCING REACTIONS OF AscoRB1c Acm

(a) To 10 ml. of a 0.01% solution of 2,6-dichlorophenol indophenol add a few drops of glacial acetic acid until the red acid colour of the indicator persists. To this liquid add 1 ml. orange juice. Conclusion? Equations? ( b) Dissolve sufficient crystalline Vitamin C to cover the end of a knife blade in 5 ml. water and add 0.5% iodine solution, drop by drop, until 1 ml. has been added. Conclusion? Equation?

75

( c) Repeat ( b) but this time use tenth normal potassium permanganate acidified with H2SO4 instead of iodine, adding it drop by drop as long as it is decolorized. This oxidation disrupts the Vitamin C molecule at the endiol double bond. Equation? Note the quantity of permanganate necessary, and draw appropriate conclusions. 107.

HYDROLYSIS OF GUMS

To separate portions of about 0.1 g. gum acacia and 0.1 g. gum tragacanth add 5 ml. concentrated hydrochloric acid and heat for five minutes on the water bath. When cool, place about 10 drops of each separately in an evaporating dish, and to this with stirring, add freshly distilled aniline, one drop at a time, until about 5 drops have been added. Conclusion? What are the carbohydrates obtained on hydrolysis? They dehydrate to furfural or derivatives which give colour reactions with aromatic amines and phenols. Equations?

108.

TEST FOR LIGNIN AND GuMs IN

Woon

With a stirring rod touch ( i) a 5% solution of resorcinol in concentrated hydrochloric acid and (ii) a 5% solution of aniline in hydrochloric acid separately to a piece of newsprint. Do likewise to a piece of filter paper. Explain the results of the experiment. Discuss, with formulas, some of the products derived from lignin and account for the probable parent structure assigned. What is the significance of the above experiment in respect to the chemical reactions involved in the manufacture of a fine paper such as filter paper on the one hand and a type of paper such as Kraft or newsprint on the other hand? List the processes involved in converting wood into a high grade paper.

AMINES 109.

DECOMPOSITIONS OF AN AMINE SALT

Mix intimately 0.5 g. of ethylamine hydrochloride and 1 g. of calcium hydroxide. Put this mixture in a test tube and warm it gently with a free flame. Note the odours of the vapours evolved. Are they flammable? Hold a moist red litmus paper and then a rod dipped in hydrochloric acid near the mouth of the tube. Write equations for all the reactions involved. ll0.

BASICITY OF AN AQUEOUS SOLUTION OF PROPYLAMINE

Into each of five test tubes pour 5 ml. of a 5% aqueous solution of propylamine. (a) Smell the first portion and test it with Alkacid paper. To the remaining four tubes add respectively 10 drops of 5% solutions of the following: ( b) ferric chloride, ( c) chromium sulphate, ( d) aluminium chloride, ( e) copper sulphate. To ( e), add a further 5 ml. of propylamine solution and note the complex ion formation.

75

( c) Repeat ( b) but this time use tenth normal potassium permanganate acidified with H2SO4 instead of iodine, adding it drop by drop as long as it is decolorized. This oxidation disrupts the Vitamin C molecule at the endiol double bond. Equation? Note the quantity of permanganate necessary, and draw appropriate conclusions. 107.

HYDROLYSIS OF GUMS

To separate portions of about 0.1 g. gum acacia and 0.1 g. gum tragacanth add 5 ml. concentrated hydrochloric acid and heat for five minutes on the water bath. When cool, place about 10 drops of each separately in an evaporating dish, and to this with stirring, add freshly distilled aniline, one drop at a time, until about 5 drops have been added. Conclusion? What are the carbohydrates obtained on hydrolysis? They dehydrate to furfural or derivatives which give colour reactions with aromatic amines and phenols. Equations?

108.

TEST FOR LIGNIN AND GuMs IN

Woon

With a stirring rod touch ( i) a 5% solution of resorcinol in concentrated hydrochloric acid and (ii) a 5% solution of aniline in hydrochloric acid separately to a piece of newsprint. Do likewise to a piece of filter paper. Explain the results of the experiment. Discuss, with formulas, some of the products derived from lignin and account for the probable parent structure assigned. What is the significance of the above experiment in respect to the chemical reactions involved in the manufacture of a fine paper such as filter paper on the one hand and a type of paper such as Kraft or newsprint on the other hand? List the processes involved in converting wood into a high grade paper.

AMINES 109.

DECOMPOSITIONS OF AN AMINE SALT

Mix intimately 0.5 g. of ethylamine hydrochloride and 1 g. of calcium hydroxide. Put this mixture in a test tube and warm it gently with a free flame. Note the odours of the vapours evolved. Are they flammable? Hold a moist red litmus paper and then a rod dipped in hydrochloric acid near the mouth of the tube. Write equations for all the reactions involved. ll0.

BASICITY OF AN AQUEOUS SOLUTION OF PROPYLAMINE

Into each of five test tubes pour 5 ml. of a 5% aqueous solution of propylamine. (a) Smell the first portion and test it with Alkacid paper. To the remaining four tubes add respectively 10 drops of 5% solutions of the following: ( b) ferric chloride, ( c) chromium sulphate, ( d) aluminium chloride, ( e) copper sulphate. To ( e), add a further 5 ml. of propylamine solution and note the complex ion formation.

77 Tabulate the results and draw conclusions. Write electronic formulas for the products formed in (a), ( b) and ( e )both parts. 111.

PREPARATION OF ANILINE

Place 2 ml. of nitrobenzene in a small Erlenmeyer flask with about 2 g. of granulated tin. Now add gradually, in small portions, about 10 ml. concentrated hydrochloric acid, shaking well after each addition. Finally heat on a water bath with frequent shaking until the oily layer of nitrobenzene has disappeared. Dilute to about twice its volume with distilled water and make distinctly alkaline with sodium hydroxide. What is the precipitate which is first formed when the reduction produce is made alkaline? Transfer the liquid to a 150 ml. distilling flask. Distil about 15 ml. from this liquid adding a piece of unglazed porcelain to it. On distilling the distillate will be an emulsion of aniline and water and oily drops of aniline may be seen. Save this liquid for future experiments. This is known as "steam distillation." Write the equations for the reduction of nitrobenzene. How is the aniline set free from this preparation? In which organic family would you place aniline? To 5 ml. of the emulsion add 5 ml. of dilute hydrochloric acid. Write the equation for the reaction. Explain the principle of co-distillation and, in particular, "steam distillation." Assuming aniline and water to be completely immiscible, calculate the %W /W of aniline in the distillate. 112.

REACTION OF ANILINE WITH BROMINE WATER

To 5 ml. of a dilute aqueous solution of aniline, add bromine water drop by drop, until about 10 drops have been added. Equation? Compare the enhanced activity shown here with that of phenol ( Exp. 66) and explain it. 113.

REAcnoN OF ANILINE WITH NITRous Aero

(a) At room temperature ( Van Slyke) Dissolve about 0.5 ml. aniline in 15 cc. of dilute hydrochloric acid. Equations? Add 5 ml. of a 10% solution of sodium nitrite. Shake and warm gently. Observe that a gas is given off, and note the odour of the solution. Equations? Repeat the experiment wtih methylaniline. ( b) At 0° (Griess) To 10 drops of aniline in a test tube add 5 ml. of dilute hydrochloric acid and cool in an ice bath. Add, with shaking, two-thirds of this solution to 5 ml. of freshly prepared 10% sodium nitrite solution previously cooled in an ice bath. Divide this liquid into two equal parts. ( i) To one half add the unused third of the aniline hydrochloride. (ii) To the other half add a solution prepared by dissolving sufficient ,8-naphthol to cover a ten-cent piece in 5 ml. of reagent sodium hydroxide. Discuss the chemistry of the reactions in (a) and ( b). Write equations. Of what significance are these reactions in dye stuff manufacture?

79 113A. PREPARATION OF ANILINE BENZENESULPHONAMIDE (FUME HOOD!) To 0.3 ml. of aniline add 4 ml. 10% NaOH and 0.4 ml. of benzenesulphonyl chloride. Stopper the tube and shake vigorously. After the chloride has reacted cool the solution and filter off the residue. Determine its m.p. ( Schotten-Baumann reaction). 114. THE IsocYANIDE (IsoNITRILE) REACTION WITH ANILINE Heat a few drops of the aniline emulsion ( Exp. 111) with a few drops of chloroform, 1 ml. reagent sodium hydroxide and 2 ml. of alcohol, in the fume cupboard. CAUTIOUSLY note the odour of the product which is a carbylamine or an isocyanide. The carbylamine reaction is given by primary amines only, and is readily recognizable by the nauseating odour. Carbylamines are extremely toxic! Equation? 115. IONIZATION OF QUATERNARY AMMONIUM HYDROXIDES AS STRONG BASES Test (a) 5 ml. of a 5% aqueous solution of tetraethyl ammonium hydroxide with Universal Indicator and ( b) 5 ml. of 5% aqueous choline with Alkacid paper. Calculate Kion for (a). Draw conclusions. 116. FORMATION OF A METAL CHELATE To 5 ml. of 5% nickel nitrate solution add dilute ( 5-10%) ammonium hydroxide solution until the complex ammoniated ion is formed ( dark blue). Then add 10-20 drops of an alcoholic solution of dimethyl glyoxime and stir. Write formulas and explain colour changes.

ANILINE DYES 117. OXIDATION OF ANILINE

(a) With Hypochlorites to give an Indamine To 5 ml. of an aqueous solution of aniline, add 5 ml. of a dilute aqueous solution of a calcium hypochlorite. The coloured substance is Indamine. Equation? Compare this structure with that of indophenol ( Exp. 71). ( b) With Dichromate to give Emeraldine To 40 ml. of an aqueous solution of aniline, add 10 ml. dilute sulphuric acid and sufficient sodium dichromate to cover the end of a knife blade. Observe over the course of 20 minutes. The green dye is Emeraldine. Formula? ( c) Oxidation of Aniline to give Aniline Black In an evaporating dish place 15 drops of concentrated sulphuric acid and 10 drops of sodium dichromate solution. Add 1 drop of aniline, stir and warm gently over a beaker of boiling water. Observe the Indamine and Emeraldine stages. Aniline Black was formerly a favourite dye for wool.

79 113A. PREPARATION OF ANILINE BENZENESULPHONAMIDE (FUME HOOD!) To 0.3 ml. of aniline add 4 ml. 10% NaOH and 0.4 ml. of benzenesulphonyl chloride. Stopper the tube and shake vigorously. After the chloride has reacted cool the solution and filter off the residue. Determine its m.p. ( Schotten-Baumann reaction). 114. THE IsocYANIDE (IsoNITRILE) REACTION WITH ANILINE Heat a few drops of the aniline emulsion ( Exp. 111) with a few drops of chloroform, 1 ml. reagent sodium hydroxide and 2 ml. of alcohol, in the fume cupboard. CAUTIOUSLY note the odour of the product which is a carbylamine or an isocyanide. The carbylamine reaction is given by primary amines only, and is readily recognizable by the nauseating odour. Carbylamines are extremely toxic! Equation? 115. IONIZATION OF QUATERNARY AMMONIUM HYDROXIDES AS STRONG BASES Test (a) 5 ml. of a 5% aqueous solution of tetraethyl ammonium hydroxide with Universal Indicator and ( b) 5 ml. of 5% aqueous choline with Alkacid paper. Calculate Kion for (a). Draw conclusions. 116. FORMATION OF A METAL CHELATE To 5 ml. of 5% nickel nitrate solution add dilute ( 5-10%) ammonium hydroxide solution until the complex ammoniated ion is formed ( dark blue). Then add 10-20 drops of an alcoholic solution of dimethyl glyoxime and stir. Write formulas and explain colour changes.

ANILINE DYES 117. OXIDATION OF ANILINE

(a) With Hypochlorites to give an Indamine To 5 ml. of an aqueous solution of aniline, add 5 ml. of a dilute aqueous solution of a calcium hypochlorite. The coloured substance is Indamine. Equation? Compare this structure with that of indophenol ( Exp. 71). ( b) With Dichromate to give Emeraldine To 40 ml. of an aqueous solution of aniline, add 10 ml. dilute sulphuric acid and sufficient sodium dichromate to cover the end of a knife blade. Observe over the course of 20 minutes. The green dye is Emeraldine. Formula? ( c) Oxidation of Aniline to give Aniline Black In an evaporating dish place 15 drops of concentrated sulphuric acid and 10 drops of sodium dichromate solution. Add 1 drop of aniline, stir and warm gently over a beaker of boiling water. Observe the Indamine and Emeraldine stages. Aniline Black was formerly a favourite dye for wool.

81 What type of chromophore group is held responsible for the colour of all products formed in this experiment? 118. THE LIEBERMANN NITROSO REACTION Put a pinch of sodium nitrite in a test tube and add 3 ml. concentrated sulphuric acid. Then add a pinch of phenol and shake. Pour a few drops of the liquid into 10 ml. of water. Make this dilute solution alkaline with sodium hydroxide solution. This test, which is probably of the IndophenolIndamine type, is given by phenols having the para hydrogen unsubstituted, also by nitrosophenols and nitrosamines. Write a reasonable structure for the coloured substance in the case investigated. 119. PREPARATION OF MAUVE-PERKIN'S HISTORIC EXPERIMENT In a test tube, mix 2 drops of aniline, a few drops of o-toluidine and a pinch of p-toluidine. Add 5 drops concentrated hydrochloric acid and 15 ml. of 5% chromic acid solution. ,varm in a beaker of boiling water for about five minutes. Dilute about 5 ml. of this liquid with water until the colour of the dye is discernible. Describe its colour. Write the formula assigned to Magenta ( Fuchsin) and indicate thereon the portion formed by each of the three amines. What was the function of the chromic acid in the reaction? How does Mauve compare structurally with Gentian Violet ( Methyl Violet)? Write the structures for ( i) the carbinol or "colour base" ( rosaniline) and (ii) the triphenylmethane derivative or "leuco base" of Methyl Violet. 120. SYNTHESIS OF AN Azo DYE ( P) Dissolve 0.5 g. sulphanilamide in 10 ml. dilute sulphuric acid and 10 ml. water. Dissolve 0.3 g. sodium nitrite in 10 ml. cold water. Keeping both solutions cold slowly run the sodium nitrite solution into the sulphanilamide solution. This process is known as the "DIAZOTIZATION." Prepare 0.4 g. beta-naphthol in 70 ml. reagent sodium hydroxide solution and run the diazotized liquid into this with stirring. This process is known as "coupling." The sodium salt of the dye is formed. Save half of this liquid for the experiment in the next paragraph. Make the other half distinctly acid. The free phenol of the dye is regenerated. Allow this to coagulate. Filter, air-dry and hand in. Which has the more intense colour, the free phenol or its salt? Dye a piece of cotton by immersing a portion of cloth about 6" x 6" in the solution of the sodium salt of the dye, allowing it to stay there for 5 minutes and then placing it in about 50 ml. dilute hydrochloric acid for 2 minutes and finally squeezing out any excess liquid and allowing to dry. Paste a portion of this dyed cloth in your note book. Write the equations for the reactions involved in the formation of the dye. Compare its structure with Prontosil and discuss briefly the therapeutic history of the latter.

83 What is the chromophore group here? Show that the benzenesulphonamido structure is also common to the chloramines ( see Exp. 133). Write the formula for Methyl Orange and indicate the structural changes in the dye when used as an indicator, i.e., how its structure changes with changes in pH. Write the formula for Congo Red and indicate how it is prepared by a method similar to that used in this experiment. Show that the trypanocidal stains Trypan Red and Trypan Blue (Merck's Index) are derivatives of the same structure as Congo Red. Make a tabulation of the different types of coloured substances which you have prepared in the laboratory, indicating the chromophore groups and a named representative of each type.

PROTEINS 121.

BrnRET REACTION

Heat about 0.5 g. urea in a small test tube until bubbles of gas are seen escaping, then hold a piece of moist red litmus in the test tube. Cool, add 5 ml. 20% sodium hydroxide solution, then 5 drops of 1% copper sulphate solution. This colour reaction is known as the biuret reaction and is given by substances whose structures contain two or more peptide linkages. Write equations for the heating of urea as above, and indicate the peptide linkages in the products. To 1 ml. of casein suspension, add 3 ml. of a 20% sodium hydroxide solution, shake, and add 5 drops of a 1% copper sulphate solution. What do you conclude?

122.

XANTHOPROTEIC REACTION

To 2 ml. of the egg albumin or casein suspension, add 3 drops of concentrated nitric acid, and allow to stand for five minutes. Then heat to boiling. Cool and make alkaline with ammonium hydroxide or sodium hydroxide solution. Record all your observations. This test indicates the presence of the phenyl-particularly a hydroxy- or amino-phenyl-group in a protein. What type of reaction is it? 123.

HOPKINS-COLE REACTION-TEST FOR TRYPTOPHANE RING

To 2 ml. of casein suspension, add 5 drops of Hopkins-Cole reagent ( glyoxylic acid). Mix well, then pour down the side of the tube, 3 ml. concentrated sulphuric acid so that two layers are formed. Observe at the end of several minutes. Write the structure for tryptophane. Construct a chart showing the other stages in the oxidation of ethylene glycol as well as the glyoxylic acid stage.

83 What is the chromophore group here? Show that the benzenesulphonamido structure is also common to the chloramines ( see Exp. 133). Write the formula for Methyl Orange and indicate the structural changes in the dye when used as an indicator, i.e., how its structure changes with changes in pH. Write the formula for Congo Red and indicate how it is prepared by a method similar to that used in this experiment. Show that the trypanocidal stains Trypan Red and Trypan Blue (Merck's Index) are derivatives of the same structure as Congo Red. Make a tabulation of the different types of coloured substances which you have prepared in the laboratory, indicating the chromophore groups and a named representative of each type.

PROTEINS 121.

BrnRET REACTION

Heat about 0.5 g. urea in a small test tube until bubbles of gas are seen escaping, then hold a piece of moist red litmus in the test tube. Cool, add 5 ml. 20% sodium hydroxide solution, then 5 drops of 1% copper sulphate solution. This colour reaction is known as the biuret reaction and is given by substances whose structures contain two or more peptide linkages. Write equations for the heating of urea as above, and indicate the peptide linkages in the products. To 1 ml. of casein suspension, add 3 ml. of a 20% sodium hydroxide solution, shake, and add 5 drops of a 1% copper sulphate solution. What do you conclude?

122.

XANTHOPROTEIC REACTION

To 2 ml. of the egg albumin or casein suspension, add 3 drops of concentrated nitric acid, and allow to stand for five minutes. Then heat to boiling. Cool and make alkaline with ammonium hydroxide or sodium hydroxide solution. Record all your observations. This test indicates the presence of the phenyl-particularly a hydroxy- or amino-phenyl-group in a protein. What type of reaction is it? 123.

HOPKINS-COLE REACTION-TEST FOR TRYPTOPHANE RING

To 2 ml. of casein suspension, add 5 drops of Hopkins-Cole reagent ( glyoxylic acid). Mix well, then pour down the side of the tube, 3 ml. concentrated sulphuric acid so that two layers are formed. Observe at the end of several minutes. Write the structure for tryptophane. Construct a chart showing the other stages in the oxidation of ethylene glycol as well as the glyoxylic acid stage.

85

124. TEST FOR SULPHUR IN PROTEINS To sufficient powdered casein to cover the bottom of a test tube, add 10 ml. reagent sodium hydroxide and 10 drops lead acetate solution. Carefully bring to boil and interpret the result. Write the names and formulas for three amino acids containing sulphur which result from the hydrolysis of proteins. What is the chemistry of the "Cold Wave" of hair? 125. M1LL0N's REACTION-TEST FOR HYDROXYPHENYL GROUP Heat 3 ml. of Millon's Reagent ( solution of mercuric nitrate and nitrite in dilute nitric acid) with sufficient powdered casein to cover the bottom of a test tube. The development of a red colour or precipitate is an indication of the presence of the hydroxy phenyl group. Write the structure for tyrosine and show that it contains such a group. 126. NINHYDRIN REACTION This is a very delicate test for alpha amino acids or proteins in which at least one alpha amino group is free. Allow sufficient (a) glycine and ( b) alanine to cover the bottom of a test tube to stand with 3 ml. 5% aqueous Ninhydrin Reagent ( triketohydrindene hydrate) for ten minutes and observe the development of the blue to violet-red colour in each case. Ascertain whether casein contains a sufficient number of free alpha amino groups to give this test. Approximately how many of the amino acids derived from protein hydrolysis are alpha amino acids? What is the structural relationship between nylon and a simple protein such as natural silk fibre?

AMIDES 127. AMMONOLYSIS OF AN ESTER-PREPARATION OF AcETAMIDE (P) Place 8.0 ml. of ethyl acetate and 20 ml. of concentrated ammonia ( 28%) in a corked labelled :Bask. Let stand in the wooden trays provided until the next laboratory period. Describe the changes in appearance. Place the contents of the :Bask in a small weighed evaporating dish and evaporate to one-fourth volume in a fume cupboard. Cool on ice and if the product does not solidify, evaporate off approximately 3 ml. more liquid. Hand in the solid product. Show how (a) acetic acid and ( b) acetonitrile can be prepared from acetamide? 128. THE HOFMANN DEGRADATION-PREPARATION OF METHYLAMINE (P)

In a 50 ml. distilling :Bask, place 8 ml. of 30% sodium hydroxide solution, and cool well in ice-water. Then, in the hood, add through a funnel, 1 ml. bromine ( CAUTION! GOGGLES!). Shake, and cool again in ice-water. Then add 1 g. acetamide, stopper with a cork, and allow the end of the side arm to dip

85

124. TEST FOR SULPHUR IN PROTEINS To sufficient powdered casein to cover the bottom of a test tube, add 10 ml. reagent sodium hydroxide and 10 drops lead acetate solution. Carefully bring to boil and interpret the result. Write the names and formulas for three amino acids containing sulphur which result from the hydrolysis of proteins. What is the chemistry of the "Cold Wave" of hair? 125. M1LL0N's REACTION-TEST FOR HYDROXYPHENYL GROUP Heat 3 ml. of Millon's Reagent ( solution of mercuric nitrate and nitrite in dilute nitric acid) with sufficient powdered casein to cover the bottom of a test tube. The development of a red colour or precipitate is an indication of the presence of the hydroxy phenyl group. Write the structure for tyrosine and show that it contains such a group. 126. NINHYDRIN REACTION This is a very delicate test for alpha amino acids or proteins in which at least one alpha amino group is free. Allow sufficient (a) glycine and ( b) alanine to cover the bottom of a test tube to stand with 3 ml. 5% aqueous Ninhydrin Reagent ( triketohydrindene hydrate) for ten minutes and observe the development of the blue to violet-red colour in each case. Ascertain whether casein contains a sufficient number of free alpha amino groups to give this test. Approximately how many of the amino acids derived from protein hydrolysis are alpha amino acids? What is the structural relationship between nylon and a simple protein such as natural silk fibre?

AMIDES 127. AMMONOLYSIS OF AN ESTER-PREPARATION OF AcETAMIDE (P) Place 8.0 ml. of ethyl acetate and 20 ml. of concentrated ammonia ( 28%) in a corked labelled :Bask. Let stand in the wooden trays provided until the next laboratory period. Describe the changes in appearance. Place the contents of the :Bask in a small weighed evaporating dish and evaporate to one-fourth volume in a fume cupboard. Cool on ice and if the product does not solidify, evaporate off approximately 3 ml. more liquid. Hand in the solid product. Show how (a) acetic acid and ( b) acetonitrile can be prepared from acetamide? 128. THE HOFMANN DEGRADATION-PREPARATION OF METHYLAMINE (P)

In a 50 ml. distilling :Bask, place 8 ml. of 30% sodium hydroxide solution, and cool well in ice-water. Then, in the hood, add through a funnel, 1 ml. bromine ( CAUTION! GOGGLES!). Shake, and cool again in ice-water. Then add 1 g. acetamide, stopper with a cork, and allow the end of the side arm to dip

87 into 10 ml. of distilled water in an open test tube. Heat carefully with a small, moving flame until the mixture becomes clear and colourless and a vigorous evolution of vapours ensues. Remove the flame from time to time until the main action has subsided. Compare the odour of the fumes with that of ammonia. Test the flammability of some of the gas. Test the reaction of the aqueous distillate to red litmus. Why is the reaction termed a degradation? Add 1 ml. of the distillate to 1 ml. of a 5% solution of ferric chloride. Equation? Add 1 ml. of the distillate to 1 ml. of 0.3% copper sulphate solution. Equation? To the remainder of the distillate add 10 ml. of a saturated aqueous solution of picric acid, evaporate to half volume, cool and allow to stand covered with a watch glass until the next laboratory period. Filter off the amine picrate and hand it in. The formation of crystalline picrates with sharp melting points is a general reaction of organic bases. Equation? 0

129. IsoMERIZATION OF AMMONIUM CYANATE TO UREA-WOHLER's HISTORIC EXPERIMENT ( p)

In an evaporating dish, place 5.0 g. potassium cyanate, 7.0 g. ammonium sulphate and 30 ml. water, and evaporate to dryness on a water-bath. The relatively low solubility of K2S04 makes this salt precipitate out, producing a practically complete reaction. ·when it forms a scum on the surface of the liquid, it will be necessary to stir occasionally. The heat induces the isomerization. Take the powdered dry solid from the evaporating dish and place it in a 250 ml. Erlenmeyer. Add 50 ml. of 95% ethanol and heat for 5 minutes under reflux in a beaker half-full of water nearly at the boil. This procedure will extract the urea, but not the inorganic salts. Filter quickly while hot into an exaporating dish and leave it to evaporate until the next laboratory period. Hand in the specimen. Show that the product contains urea by subjecting a portion of it to the biuret test ( Exp. 121). Indicate the result of this test on the label. What reactions of urea make it useful as a fertilizer and as an alkaliforming dentrifice? How is urea synthesized commercially? What is the formula for ANTU, the rodenticide? Write the formulas of urethane, ammonium carbamate and thiourea.

130. DECOMPOSITION oF UREA BY Nirnous Acm To 3 or 4 ml. of an aqueous solution of urea ( 1 g. of urea to 10 ml. of water) in a test tube, add 2 or 3 ml. of dilute hydrochloric acid and 1 ml. of a 10% solution of sodium nitrite. Write an equation for the reaction. 131. SEMI-MICRO PREPARATION OF AcETANILIDE (ANTIFEBRIN) (P)

In a fume cupboard, to 10 drops of aniline in a small test tube ( 1 x 10 cm. ) , add carefully 2 ml. of acetic anhydride drop by drop, and shake or stir for 5 minutes. Allow to stand for 15 minutes. CAUTION: no NOT

INHALE II

+

89

Add 3 ml. water 2 ml. ethanol and heat until a clear solution results adding more hot water if necessary. Allow to cool slowly first in the room and then in an ice bath for 5 minutes. Equation? Filter through a Hirsch funnel fitted into a side arm test tube. Air-dry, and hand in. 132. ScHOITEN-BAUMANN REACTION-PREPARATION OF H1PPURIC Acrn (P)

In a small Erlenmeyer dissolve 0.6 g. glycine in 8 ml. 20% aqueous sodium hydroxide solution. Cautiously in a fume cupboard, add 1.0 ml. benzoyl chloride, shaking vigorously until one phase is formed. At the end of one hour, pour the liquid with vigorous stirring into a mixture of 25 ml. ice water and 10 ml. concentrated hydrochloric acid. Filter the precipitate on a Hirsch funnel ( see above), wash twice with 5 ml. cold water, and allow to dry in the air. Write the equation and hand in the sample. 133. Cm...ORAMIDES ("CHLORAMINEs") AS A STABLE SOURCE OF AVAILABLE CHLORINE

Prepare 25 ml. of starch-iodide liquid by dissolving a few small crystals of potassium iodide in 25 ml. of starch suspension. Into this liquid drop a tablet, or if in powdered form, sufficient of one of the Chloramines to cover a ten cent coin. Acidify with 5 ml. dil. HCI. Allow to stand for about five minutes, then stir the liquid. Conclusions? Write the formulas for Chloramine-T, Dichloramine-T and Halazone in such a manner as to show the similarity. What are some of the uses of these substances?

HETEROCYCLIC COMPOUNDS 134. DEHYDRATION OF Muc1c Acrn-PREPARATION OF FuRAN D1cARBOXYLIC Acrn-2,5 (P)

To 1 g. mucic acid ( prepared in Experiment 105) add 5 ml. concentrated hydrochloric acid in a small test tube and warm in a water-bath at 90°-100° for 10 minutes. Allow to settle, pour off as much of the supernatant hydrochloric acid as convenient, add 15 ml. water, stir and filter on a Hirsch funnel. Dry the product and hand it in. Equation? Alternative name for product? 135. FuRFURALDEHYDE-AN UNSATURATED ALDEHYDE

(a) To 5 ml. of furfuraldehyde ( furfural) add dropwise, 10 drops of a 5% solution of bromine in carbon tetrachloride. ( b) Boil 10 drops of furfural with 10 ml. of combined Fehling's solutions, "A" and "B." Write equations for the above reactions. How is furfural prepared commercially? Note the colour tests for furfural in the experiments on the hydrolysis of pentosans ( Exp. 107, 108).

INHALE II

+

89

Add 3 ml. water 2 ml. ethanol and heat until a clear solution results adding more hot water if necessary. Allow to cool slowly first in the room and then in an ice bath for 5 minutes. Equation? Filter through a Hirsch funnel fitted into a side arm test tube. Air-dry, and hand in. 132. ScHOITEN-BAUMANN REACTION-PREPARATION OF H1PPURIC Acrn (P)

In a small Erlenmeyer dissolve 0.6 g. glycine in 8 ml. 20% aqueous sodium hydroxide solution. Cautiously in a fume cupboard, add 1.0 ml. benzoyl chloride, shaking vigorously until one phase is formed. At the end of one hour, pour the liquid with vigorous stirring into a mixture of 25 ml. ice water and 10 ml. concentrated hydrochloric acid. Filter the precipitate on a Hirsch funnel ( see above), wash twice with 5 ml. cold water, and allow to dry in the air. Write the equation and hand in the sample. 133. Cm...ORAMIDES ("CHLORAMINEs") AS A STABLE SOURCE OF AVAILABLE CHLORINE

Prepare 25 ml. of starch-iodide liquid by dissolving a few small crystals of potassium iodide in 25 ml. of starch suspension. Into this liquid drop a tablet, or if in powdered form, sufficient of one of the Chloramines to cover a ten cent coin. Acidify with 5 ml. dil. HCI. Allow to stand for about five minutes, then stir the liquid. Conclusions? Write the formulas for Chloramine-T, Dichloramine-T and Halazone in such a manner as to show the similarity. What are some of the uses of these substances?

HETEROCYCLIC COMPOUNDS 134. DEHYDRATION OF Muc1c Acrn-PREPARATION OF FuRAN D1cARBOXYLIC Acrn-2,5 (P)

To 1 g. mucic acid ( prepared in Experiment 105) add 5 ml. concentrated hydrochloric acid in a small test tube and warm in a water-bath at 90°-100° for 10 minutes. Allow to settle, pour off as much of the supernatant hydrochloric acid as convenient, add 15 ml. water, stir and filter on a Hirsch funnel. Dry the product and hand it in. Equation? Alternative name for product? 135. FuRFURALDEHYDE-AN UNSATURATED ALDEHYDE

(a) To 5 ml. of furfuraldehyde ( furfural) add dropwise, 10 drops of a 5% solution of bromine in carbon tetrachloride. ( b) Boil 10 drops of furfural with 10 ml. of combined Fehling's solutions, "A" and "B." Write equations for the above reactions. How is furfural prepared commercially? Note the colour tests for furfural in the experiments on the hydrolysis of pentosans ( Exp. 107, 108).

91 136.

DEHYDRATION AND DECARBOXYLATION OF Muc1c

Aero

(P)

Using a fish-tail burner top, bend an ordinary test tube at the middle so that it makes a right angle. Place 6 g. of mucic acid in this test tube. Clamp the tube near the mouth in such a way that the open end dips slightly downward. Carefully heat the mucic acid by running a small flame up and down the tube until all water has been driven off. Then distil rapidly and catch the distillate in an evaporating dish. Give three alternative names for the product. Equation? How could furoic acid be turned into furane? Hand in the product. It may be slightly charred. 137.

FORMATION OF PYRROLE

In an evaporating dish place about 0.5 g. mucic acid with 5 ml. concentrated ammonium hydroxide and carefully evaporate to dryness under a hood. Scrape the ammonium mucate from the dish and transfer it to a test tube. Heat strongly, and suspend in the tube a soft pine splinter which has previously been soaked in concentrated hydrochloric acid for several minutes. This colour test is a very delicate reaction for pyrrole. When the ammonium salts of the six-carbon, dibasic sugar-acids are heated, they cyclize into pyrrole by dehydration, decarboxylation and deammonation. Write the equation for the formation of the pyrrole in this experiment. Write the formulas and names of the completely reduced derivatives of pyrrole and of pyridine.

0

138.

PREPARATION OF A PYRROLE DERIVATIVE-COPPER PHTHALOCYANINE ( MoNASTRAL BLUE) (

P)

In a 50 ml. Erlenmeyer flask, place 6 g. urea and 0.2 g. boric acid and support the flask in a suitable Pyrex beaker containing a liquid mixture of orthophosphoric and metaphosphoric acids. Raise the temperature of this bath to 200°-220°C and as soon as the urea commences to soften ( 110°-120° ), add a powdered mixture of 4 g. phthalic anhydride ( or phthalimide) and 1.0 g. cupric chloride dihydrate. Stir and poke down with the stirring rod, any material from around the top and sides of the Erlenmeyer, and keep the inside temperature at 210°. Assume a 10° lag between inside and outside temperatures. When the frothing due to the evolution of water and ammonia has subsided, heat carefully at 200°-210° until the melt is dry. Remove the crude pigment and hand it in without powdering. What are some of the impurities present? Do NOT COOL THE THERMOMETER IN WATER!!

Write the electronic representation for the central portion of the structure of copper phthalocyanine. What is meant by chelation? Compare the structures of haemin, chlorophyll ( "a" or "b") and the phthalocyanines. Note their similarities and indicate the chromophoric portions of each. Write out the structural portion which is common to all.

93

Give formulas and names for two other types of chelated structures, one of which involves hydrogen bonding. 0

139. PREPARATION OF PHTHALIMIDE (P)

Mix well, by grinding in a mortar, 5 g. of phthalic anhydride and 8 g. of ammonium carbonate. Transfer to a large test tube and heat gradually over a free flame, moving the tube up and down through the flame. Water will first condense in the cold part of the tube, then white fumes of phthalic anhydride will be given off and finally this will cease when the mass in the test tube has become molten ( about 15 minutes). Any sublimate should be pushed down with a stirring rod. Pour this molten mass into a cold evaporating dish, allow to cool and then scrape off the sublimate of unchanged phthalic anhydride from the top of the solid mass. Powder the remainder of the solid. Take sufficient of the powdered solid to cover a ten-cent piece and test its solubility in reagent sodium hydroxide solution. Equation? Hand in the remainder. Write equations for all the reactions involved. Show by formulas that phthalic anhydride can be considered to be a derivative of a tetrahydrofurane and phthalimide a derivative of tetrahydropyrrole ( pyrrolidine). 0

140. PREPARATION OF HYDANTOIN (P)

Mix well, by grinding in a mortar, 5.0 g. of urea and 5.0 g. of glycine. Transfer the mixture to a large Pyrex test tube and stand it in a phosphoric acid bath so that at least one-third of the tube is immersed. Suspend a thermometer in the bath, raise the temperature to 125° and hold it at 125°-130° as long as ammonia is being evolved (litmus). The spongy, viscous solid must be pushed down the tube from time to time with a stirring rod or a nichrome spatula. When the evolution of ammonia has ceased ( about 45 minutes) and the mass has become rigid, remove the tube from the bath and allow to cool to 80°-90°. The product at this stage is hydantoic acid. Dissolve it in the minimum amount of hot water, then concentrate in an evaporating dish by evaporation to about 20 ml., cool, add 20 ml. concentrated hydrochloric acid and heat until the volume is about 25 ml. Cool in an ice bath for 10 minutes, filter, air-dry, and hand in. Write equations for all reactions involved. 0

141. PREPARATION OF PHENOTIIlAZINE (P)

Grind intimately in a mortar 5.0 g. of diphenylamine and 2.0 g. of sulphur. Transfer this powder along with a pinch of iodine to a test tube and heat carefully until the system melts and bubbles are evolved ( about 180°C). At this stage hold at the mouth of the tube a strip of filter paper dipped in lead acetate solution. Conclusion? Continue heating as long as a copious quantity of bubbles is being evolved. When this reaction becomes slow and white fumes begin to issue

95 from the mouth of the tube ( 15 to 20 minutes) discontinue the heating and pour the melt in a thin layer into an evaporating dish. Cool this in ice, detach the solidified crude product, powder it and hand in. Write an equation for the reaction. What colour would you expect the product to be when pure? Give reasons for your answer. Show that Methylene Blue and Chlorpromazine are derivatives of phenothiazine.

IDENTIFICATION OF ORGANIC COMPOUNDS 142

In this part of the work only single pure compounds ( liquid or solid) will be used as unknowns. In practice, mixtures are often encountered which must be separated into their constituents and these in turn must be purified by crystallization and distillation. The following procedures must be followed systematically and all the observations carefully recorded. A derivative must be prepared and its m.p. determined. 1. Preliminary Examination Record the physical state, colour, and odour of the unknown. Perform an ignition test by heating 0.2 g. of the material on a spatula ( Exp. 12). Does it burn? Does it melt? Are any vapours evolved? Do they smell? Is there a residue? Test the solubility of the residue in water and the acidity of the solution. Is a gas evolved from the residue when 1-2 drops of HCl is added to it? 2. Physical Constants Determine the melting point of the unknown if it is a solid ( Exp. 2) or its boiling point ( Exp. 5) if it is a liquid. For solids which melt above 100° use a Crisco oil bath in a 50 ml. beaker. 3. Qualitative Analysis (a) Carry out a sodium fusion on a 0.1 g. sample of the unknown ( Exp. 13). Test the fission filtrate for nitrogen, sulphur and halogens. ( b) Perform the Beilstein test on a sample of the unknown ( Exp. 14). ( c) Test a 0.1 g. sample of the unknown with an alcoholic silver nitrate solution before and after boiling ( Exp. 25). ( d) Heat a 1 g. sample with 2 g. of soda-lime in a hard glass test tube and note whether or not ammonia is evolved. ( Smell? Litmus?) ( e) Test for unsaturation by the permanganate test and bromine water directly on a liquid unknown. Use alcoholic solutions ( 0.1 g. in 2 ml.) for solid unknowns ( Exp. 16). 4. Solubility Tests Determine the solubilitv of the unknown in water; ether; 5% NaOH; 5% HCl; and cold cone. sulph~ric acid. Use 0.1 g. or 0.2 ml. samples in 3 ml. of solvent added in 1 ml. portions. Shake well.

95 from the mouth of the tube ( 15 to 20 minutes) discontinue the heating and pour the melt in a thin layer into an evaporating dish. Cool this in ice, detach the solidified crude product, powder it and hand in. Write an equation for the reaction. What colour would you expect the product to be when pure? Give reasons for your answer. Show that Methylene Blue and Chlorpromazine are derivatives of phenothiazine.

IDENTIFICATION OF ORGANIC COMPOUNDS 142

In this part of the work only single pure compounds ( liquid or solid) will be used as unknowns. In practice, mixtures are often encountered which must be separated into their constituents and these in turn must be purified by crystallization and distillation. The following procedures must be followed systematically and all the observations carefully recorded. A derivative must be prepared and its m.p. determined. 1. Preliminary Examination Record the physical state, colour, and odour of the unknown. Perform an ignition test by heating 0.2 g. of the material on a spatula ( Exp. 12). Does it burn? Does it melt? Are any vapours evolved? Do they smell? Is there a residue? Test the solubility of the residue in water and the acidity of the solution. Is a gas evolved from the residue when 1-2 drops of HCl is added to it? 2. Physical Constants Determine the melting point of the unknown if it is a solid ( Exp. 2) or its boiling point ( Exp. 5) if it is a liquid. For solids which melt above 100° use a Crisco oil bath in a 50 ml. beaker. 3. Qualitative Analysis (a) Carry out a sodium fusion on a 0.1 g. sample of the unknown ( Exp. 13). Test the fission filtrate for nitrogen, sulphur and halogens. ( b) Perform the Beilstein test on a sample of the unknown ( Exp. 14). ( c) Test a 0.1 g. sample of the unknown with an alcoholic silver nitrate solution before and after boiling ( Exp. 25). ( d) Heat a 1 g. sample with 2 g. of soda-lime in a hard glass test tube and note whether or not ammonia is evolved. ( Smell? Litmus?) ( e) Test for unsaturation by the permanganate test and bromine water directly on a liquid unknown. Use alcoholic solutions ( 0.1 g. in 2 ml.) for solid unknowns ( Exp. 16). 4. Solubility Tests Determine the solubilitv of the unknown in water; ether; 5% NaOH; 5% HCl; and cold cone. sulph~ric acid. Use 0.1 g. or 0.2 ml. samples in 3 ml. of solvent added in 1 ml. portions. Shake well.

Group 1-soluble in both water and ether: lower members ( 4 carbons) of oxygen and/or nitrogen containing compounds; e.g., alcohols, esters, acids, amines, aldehydes, ketones, phenols, nitriles, anhydrides. Group 2-soluble in water but insoluble in ether: hydroxy acids, polyhydroxy alcohols ( sugars ) , amides, amino acids, sulfonic acids, salts. Group 3-insoluble in water but soluble in 5% NaOH: acids, phenols, nitro compounds. Group 4-insoluble in water but soluble in 5% HCl: amines. Group 5-compounds not containing N and S, soluble only in cone. H2SO4: unsaturated hydrocarbons, aldehydes, ketones, esters, ethers, acyl halides. Group 6-compounds not containing N or S insoluble in cone. H2SO4: hydrocarbons, aromatic and aliphatic halogen derivatives of hydrocarbons. Group 7-compounds containing N or S not in Group 1-4, soluble in cone. H2SO4: nitro compounds, amides, nitriles. 5. Special Tests for Specific Groups

( 1) Alcohols: Exps. 27, 30, 62. Derivative: 3,5-dinitrobenzoate, Exp.

34A.

(2) Phenols: Exps. 82, 72. Derivative: bromine derivative, Exp. 66. ( 3) Amines: Exp. 113 ( b). Derivatives: picrates, Exp. 20, 128 ( last par.); benzenesulphonamides, Exp. 113A. ( 4) Aldehydes and Ketones: Exps. 27, 35, 46, 51. Derivatives: hydrazones, oximes, semicarbazones. ( 5) Aromatic nitro compounds: Reduce to amine ( Exp. 111) and then follow ( 3) above. ( 6) Acids. Derivative: anilides, Exp. 56A. (7) Unsaturated Hydrocarbons: Test for unsaturation (Exp. 10).

INDEX (Numbers refer to experiments) Acenaphthene, 4 Acetaldehyde, 35, 41, 47 Acetamide, 127 Acetanilide, 56A, 131 Acetic acid, 27, 52, 54 Acetoacetic ester, 80, 81, 82 Acetone, 34, 35, 45, 46, 58, 79 Acetophenone, 33, 46 Acetyl acetone, 82 Acetyl salicylic acid, 63 Acids, 52, 55 Acrolein, 39 Additional reaction, 45 Aerosol O.T., 60 Alanine, 126 Aldehydes, 35 Aldol reaction, 42 Aminophenol, 69 Ammonolysis, 127 Ammonium cyanate, 129 Amyl bromide, 14 Amylene, 16 Aniline, 111, 112, 113, 117 Aniline black, 117 Anthraquinone, 84 Anthracene picrate, 20 Antifebrin, 131 Aromatic free radical, 24 Ascorbic acid, 106 Aspirin, 63 Autooxidation, 48 Azo dye, 120 Baeyer's test, 16 Beilstein test, 13 Benedict test, 97, Benzaldehyde, 48, 56 Benzene,5, 16, 17, 18, 19 Benzenesulphonamide, 113A Benzoic acid, 53, 57 Benzoin, 83 Benzophenone,37,47 Benzoyl acetone, 82 Benzyl alcohol, 53, 87 Benzyl chloride, 25, 26 Biphenyl, 19 Biuret reaction, 121 Boiling point, 5 Bromofonn, 25 1 ° Butyl alcohol, 31, 32 2° Butyl alcohol, 31, 32 3° Butyl alcohol, 31, 32 1 • Butyl chloride, 26 2° Butyl chloride, 26 3 ° Butyl chloride, 26 Carbohydrates, 95-108 Carbon ( test for), 12 Carbon tetrachloride, 12 Carbylamine reaction, 114 Cellulose, 104

Cellulose acetate, 90 Cellulose hexanitrate, 102 Cellulose xanthate, 103 Chelate compounds, 116 Chloramines, 133 Chlorobenzene, 16, 25,26 Chloroform, 14, 28 Chromatography, 7, 8 Cinnamic acid, 55 Cinnamic aldehyde, 51 Citric acid, 55 Copper phthalocyanine, 138 Cupric enolate of acetoacetic ester, 80 Cyanohydrin reaction, 56 Cyclohexane, 16 Cyclohexanol, 30 Cyclohexanone, 45, 47 Cyclohexene, 16 Decarboxylation: partial, 58; total, 17 Depolymerization, 43, 91 Diazotization, 120 Dibenzalcyclohexanone, 42, 86 Dichlorobenzene ( p), 3 Dienolate of Benzoin, 83 Diethyl ketone, 27 Dimethylglyoxime, 116 Dinitrobenzene, 22 Dinitrobenzoates, 34A Diphenylcarbinol, 37 Distribution coefficient, 10 Emeraldine, 117 Enhanced activity, 66 Enolization, 84 Enols, 82 Eosin, 77 Esterification, 61, 62, 63, 98 Ethanol, 6, 12, 15, 29, 33, 38 Ethyl acetate, 27, 64 Ethylamine .HCl, 109 Ethylene, 15 Eutectic, 3 Extraction, 11 Fehling's test, 35 Fermentation, 29 Fluorescein, 74, 75, 76, 78 Fonnaldehyde,35,36,40,43 Formic acid, 55 Fractional distillation, 6 Free radicals, 24 Friedel-Crafts' reaction, 19 Fructose, 96, 97 Furan dicarboxylic acid, 134 Furfnraldehyde, 135 Furoic acid, 55, 136 Gardino!, 60 Gasoline, 16 Glucose,29,95,96, 97, 98 Glycerol, 12, 39 Glycine, 126, 132, 140

Glyptal resin, 88 Griess reaction, 113 Gum acacia, 107 Gum tragacanth, 107 Gun cotton, 102 Halochromic salts, 18 Haloform reaction, 27 Halogenation, 31 Halogens ( test for), 13, 14 Hexamethylenetetramine, 44 Hexane, 14, 16 Hippuric acid, 137 Hofmann reaction, 128 Hopkins-Cole reaction, 123 Hydantoin, 140 Hydrazones, 46 Indamine, 117 Indophenolreaction, 71 Intermolecular reaction, 15 Intramolecular reaction, 15 Inversion, 100 lodoform test, 27 Isoamyl acetate, 62 lsocyanide reaction, 114 Isopropyl alcohol, 34 Lactic acid, 55 Lactones, 74 Lactose, 96, 97, 105 Lassaigne test, 13 Liebermann nitroso reaction, 67, 118 Lignin, 108 Lucas reagent, 31 Lucite, 91 Maltose, 96, 97 Mandelic acid, 55 Mauve, 119 Melting point, 2, 3 Methanol, 27, 30, 38 Methylamine, 128 Methyl ethyl ketone, 35 Methyl methacrylate, 92 Methyl ,8-naphthyl ether, 73 Methyl salicylate, 61 Millon reaction, 125 Molecular rearrangement, 94 Molisch test, 96 Monastral blue, 138 Mucic acid, 105, 134, 136, 137 Naphthalene, 3, 18 1,4-naphthoquinone, 85 ,8-naphthol, 82 Ninhydrin reaction, 126 Nitrobenzene, 21, 23 Nitro compounds, 23 Nitrogen ( test for), 13 Nitro phenols ( o and p), 82 Nitroprusside test, 34 Nitrosation, 67, 118 Nitroso reaction, 67, 118 Nylanders test, 97 Oleic acid, 55 Osazones, 99 Oxalic acid, 55 Oxime of vanillin, 49 Oximes, 49 Paraformaldehyde, 43 1-pentene, 16 Perkin's experiment, 119

Phenols, 65, 66, 68, 82 Phenolphthalein, 72 Phenol resin, 89 Phenothiazine, 141 Phenylacetaldehyde, 35, 82 Phenylacetic acid, 55 Phthalic acid, 55 Phthalic anhydride, 138, 139 Phthalimide, 139 Picric acid, 20 Pinacol, 50 Pinacol rearrangement, 94 Polymerization, 43, 92 Polysulphide rubber, 93 2-propanol, 34 Propylamine, 110 Pyrrole, 137 Quinhydrone, 70 Quinol, 82 Recrystallization, 4 Reflux ratio, 6 Refractometry, 9 Resorcinol, 40, 82 RF value, 7 Salicylic acid, 82 Saponification, 59, 64 Saponification number, 59 Salts, 57 Schiff's test, 35 Schmidlin reaction, 24 Schotten-Baumann reaction, 113A, 132 Semicarbawnes, 51 Soap,59 Sodium acetate, 12 Starch, 101 Stearic acid, 55 Stilbenediol, 83 Sublimation, 53 Succinic acid, 55 Sucrose, 12, 94, 97, 100 Sulphanilamide, 120 Sulphur ( test for), 13 Surfactants, 60 Tartaric acid, 55 Tetrabromfluorescein, 78 Tetraethyl .NH 4 0H, 115 Tetramethylpinacol, 50, 94 Thermometer calibration, 1 Thermoplastic resin, 88 Thermosetting resin, 88 Thymol, 67 Tollens' test, 97 Toluene, 14 Toluic acid, 55 Trichloroacetic acid, 52 Triphenylmethyl chloride, 24 Tryptophane, 123 Tyrosine, 125 Unsaturation ( test for), 16 Urea, 129, 130 Urotropine, 44 Vanillin,49,82 Van Slyke reaction, 113 Vinyl chloride, 25 Viscose, 103 Williamson synthesis, 73 Wohler reaction, 129 Xanthoproteic reaction, 122