The Synthesis of Some Substituted Styrenes

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by____________________ Carl


L. Carlson





Doctor of Philosophy


r o f e s s o r in



T h e s is

May 27,_____ 19 50




SCHOOL POEM 9—3 - 4 9 —1M

THE SYNTHESIS OF SOME SUBSTITUTED STYRENES A Thesis Submitted to the Faculty of Purdue University by Carl L. Carlson In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy June, 1950

ProQuest Number: 27712263

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uest ProQuest 27712263 Published by ProQuest LLC (2019). C opyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C o d e M icroform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106 - 1346

ACKNOWLEDGMENT The author wishes to express his appreciation for the help and suggestions of Professor G. Bryant Bachman, under whose direction this work was performed. Acknowledgment is also made to the General Tire and Rubber Company and to the Purdue Research Foundation for financial support.

TABLE OF CONTENTS ABSTRACTS Syntheses with the Aid of Métallostyrenes

Page i

Thiostyrenes Behavior of Thiophenol Under Friedel-Crafts Conditions SECTION I

ix xix


Introduction Preparation of Intermediates Discussion Experimental Preparation of Alpha-Methylstyrenes Reaction of Magnesium with HalogenSubstituted Styrenes Reaction of Lithium with HalogenSubstituted Styrenes Effect of Organometa11ic-Compound formation on OC-Methylstyrene Prep, and Use of 2-(p-Bromophenyl)2-Methoxy Propane in the GrignardSynthesis SECTION II


17 18 21 23 24


Discussion Polymerization Experimental SECTION III

1 5

27 36 38


Discussion Experimental

46 50







Figure I. 2*

Page Some Syntheses of Substituted oC-Methylstyrenes


Proposed Syntheses of New Substituted. O^-Methylstyrenes



New Styrenes and ofc-Methylstyrenes



Syntheses of the New Monomers



(Contribution from the Purdue Research Foundation and the Department of Chemistry, Purdue University)


1 From the Ph. D. thesis of C. L. Carlson, Purdue University.

by G. Bryant Bachman, C. L. Carlson, and Margaret Robinson


As an extension of work previously done in this

2 laboratory on methods of synthesizing substituted styrenes , 2 Bachman et al, This Journal, 70, 622, 1772 (1948) an attempt has been made to develop syntheses involving the the use of organometallic derivatives of stfl^enes.

It was

expected that these metal derivatives could be prepared from nuclearly halogenated styrenes, and could be used like other typical Grignard reagents to introduce a variety of groups into the aromatic nucleus. Halogenated styrenes were found to react extremely sluggishly with magnesium.

The use of activated magnesium

3 Gilman and Kirby, Rec. trav. chim., 54, 577 (1935) or high boiling solvents, such as dibutyl ether did not accelerate the rate appreciably.

However, the use of a

cohalide such as methyl iodide or ethyl bromide caused the aromatic halogen to react rather promptly with the magnesium. Carbonation of the reaction mixture led to the formation of p-vinylbenzoic acid^ 4 Marvel, This Journal, 67^, 2250 (1945) in 15% yield. HC 33Ha

Ô Br

HC sCHjg

{ ¥Ï5lf 25




(2 )




Large amounts of polymeric material were also obtained. Since oC-methylstyrenes have been shown to polymerize 2 5 much less readily than the corresponding styrenes 9 , 5 Staudinger and Breusch, Ber., 62B, 442-56 (1929) an attempt was made to prepare the organometallic compounds from nuclearly halogenated o(-methylstyrenes (p-bromo- and p-iodo-c(-methylstyrenes). Here again, it was found necessary to use a cohalide to obtain reaction.

Furthermore, it was

found that lithium reacted more satisfactorily than mag­ nesium.

Hydrolysis of the products, and titration of the

resulting mixture with standard acid indicated the formation of organometallic derivatives in as high as 64% yields. However, carbonation of these derivatives gave p-isopropenylbenzoic acid^ 6 Rosicka, Ann., 219, 270 (1683)

in only 10-30% yields. CHs-CrCHg

ô X

CH 3 -0=CH 2


GH 3 -G=0H 2

£) S h°8 > ■ ( 2 ) X Xh

Again large amounts of polymeric material were formed.


of the lithium derivative with acetaldhyde or benzaldehyde gave products from which polymeric materials, only, could be isolated.

Triethyltin chloride, on the other hand, gave

p-triethyltin-oé-methylstyrene in 14.5% yield. Efforts to decrease the amounts of polymerization


occurring in these reactions were largely unsuccessful. The use of an inert atmosphere helped only a little.


addition of typical polymerization inhibitors was not practical except during isolation of the product, since these materials, themselves, react with organometallic compounds.

It was hoped that an exchange metallation

reaction could be effected between brominated styrenes and a preformed aliphatic organometallic compound.


butyllithium and p-bromo-o6rmethylstyrene mixtures, when carbonated,

gave only polymeric material and valeric

acid (50% yield).

It was concluded that the free radicals

produced during the formation of the organometallic compounds acted as powerful activators for the polymerization.


test this an experiment was run in which methyl iodide was reacted with magnesium in the presence of an equimolar amount of unsubstituted o^-methylstyrene.

Hydrolysis of the

reaction mixture led to the recovery of a 74% yield of the unsaturated dimer ofo(-methylstyrene (2,4-diphenyl-4-methyl2 -pentene)^

7 Bergmann, Taubadel, and Weiss, Ber., 64B, 1493 (1931) and some polymeric material.

A similar experiment with

lithium in place of magnesium gave comparable results. It may be concluded that the above approach to the synthesis of nuclearly substituted styrenes is not very practical.

It should be noted, however, that p-vinyl­

benzoic acid is obtained in fewer steps, and in better


overall yields by this procedure than by a previously proposed one ^ Acknowledgment. The authors are indebted to the General tire and Rubber Company and the Purdue Research Foundation for support in the form of a fellowship. Experimental Q p-Bromostyrene . 8 Quelet, Bull, soc. chim., 45, 75-97 (1929)

The addition of 54.2 g. (0.58 mole) of methyl iodide to 10 g. (0.4 mole) of magnesium in 400 ml. of ether, reaction of the product with 60 g. (0.33 mole) of p-bromobenzaldehyde9 , 9 Organic Syntheses, Col. Vol. 2 , page 89 and hydrolysis with 10 % aqueous ammonium chloride solution gave 68 g. (66 % theory) of 1 -(p-bromophenyl)ethanol (b.p. 105-107° at 2 mm.).

Dehydration of this alcohol with 4.1 g.

of potassium bisulfate and 1.0 g. of phenyl-naphthylamine at 150-180°and 80 mm. pressure gave 12.3 g. (20% theory) of the desired styrene, b.p. 56-57° (2mm.)



similar product was obtained in 2 % yield by cracking brominated polystyrene 10 , 10 Bachman and coworkers, J. Org. Chem., 12, 108 (1947) and rectifying the product.

Oxidation with potassium per­

manganate gave p-bromobenzoic acid, m.p. 250-252°.


p-Vinylbenzoic acid^

A mixture of 4.9 g. (0.027 moles)

of p-bromostyrene and 2.6 g. (0.024 mole) of ethyl bromide was reacted with 1.8 g. (0.075 mole) of activated magnesium in 55 ml. of ether.

The product was carbonated with dry

ice and then hydrolyzed with dilute sulfuric acid to obtain 0.6 g. (15% theory) of p-vinylbenzoic acid, m . p . 139-140° (from 20% ethanol).

The acid decolorized bromine and per­

manganate , was easily oxidized to terephthalic acid, m.p. 300 and gave a p-bromophenacyl ester, m.p. 10 0 - 1 0 2 °* x-Halogeno-o(rmethylstyrenes. The Grignard reagent from 99.5 g. (0.7 mole) of methyl iodide and 17 g. of magnesium was treated with 78 g. (0.3 mole) of methyl p-iodobenzoate. Hydrolysis with saturated ammonium chloride solution, isolation of the organic layer, and dehydration of the intermediate tertiary alcohol by refluxing with an excess of acetic anhydride for 20 hours gave on distillation 24.0 g. (33% theory) of the desired p-iodo-o&methylstyrene, b.p. 68-70^(2 mm.), m.p. 44°. Anal. Calcd. for C 9H 9 I: C, 44.3; H, 3.69.

Found'*'} 0,44.7,

H, 3.49. 11 Carbon and hydrogen analyses by Dr. H. Galbraith, Purdue University. The corresponding m- and p-bromo-06-methylstyrenes


12 Seymour and Wolfstein, This, Journal, 70, 1178 (1948)

were prepared by analogous methods.

The m-bromo compound,

b.p. 60-7r*(2 mm.), was obtained in 49% yield from methyl m-bromobenzoate.

The p-bromo compound, b.p. 9 5 o{10 mm.),

was obtained in 42% yield from ethyl p-bromobenzoate.


was also prepared from p-dibromobenzene, magnesium and acetone^2 in 51% yield. p-Isopropenylbenzoic acld^. (A) From p-iodo-oC— methylstyrene, and magnesium.

A mixture of 11.9 g. (0.05 m o l e )

of p-iodo-cfc-methylstyrene, 5.2 g. (0.048 mole) of ethyl bromide, 3.6 g. (0.15 mole) of activated magnesium, and 60 ml. of ether was allowed to react for two hours and then carbonated.

Hydrolysis with dilute sulfuric acid and

purification of the product by recrystallization from water gave 0.4 g. (10% theory) of white crystalline acid, m.p. 156-158° (sublimes), neutral equivalent 162.5 (calcd. 162.0), p-bromophenacyl ester, m.p. 118-121°.

Oxidation of the acid

gave terephthalic acid. (B) From p-bromo-o6-methylstyrene and lithium.


suspension of 0.7 g. (0.1 mole) of lithium in 50 ml. of ether under nitrogen was treated with a mixture of 9.85 g. (0.05 mole) of p-bromo-o(.-methylstyrene and 0.5 g. of butyl bromide in 50 ml. of ether.

After 2 hours at reflux, the

mixture was carbonated and worked up as before.

The yield

of recrystallized acid, m.p. 161-163°, was 31%. p-Triethyltin-ofcmethylstyrene.

The lithium compound

from 49.3 g. (0.25 mole) of p-bromo-o^methylstyrene and 3.47


(0,5 mole) of lithium in 160 ml. of ether was treated with 1 rz

60.4 g. (0.25 mole) of triethyltin chloride 15 Kocheshkov, J. gen. Chem. (U.S.S.R.), 4, 1359 (1934); C. A. 29, 3650 (1935) added over a period of an hour.

After 3 hours at reflux the

mixture was filtered and the liquid filtrate fractionated directly under diminished pressure.

The desired product was 25 a colorless liquid, b.p. 129-130° (2 mm.), dg^ 1.2311, 25 n%) 1.5441, yield 12.0 g. (14.5% theory). The analysis of the compound for tin followed the procedure of Gilman and King14. 14 Gilman and King, This Journal, 51, 1213 (1929) Anal. Calcd for C ^ H ^ S n :

Sn, 36.7.

Found : Sn, 37.5.

p-Triethyltin-o^methylstyrene copolymerized normally with butadiene in a typical emulsion system to give a 100 % yield of a crumbly rubber.

The polymerization was rather

slow. Effect of organometallic compound formation on o£-methylstyrene.

Methyl iodide, 71.0 g. (0.5 mole), in 75 ml. of

ether was added to a stirred mixture of oC-methylstyrene, 59 g. (0.5 mole), and magnesium, 12.0 g. (0.5 mole), in 150 ml. of ether.

When the formation of the Grignard reagent was

complete, hydrolysis was accomplished by the careful addition of saturated ammonium chloride solution.

The ether layer


was dried, and the ether removed under vacuum at room temp erature.

Distillation of the residual liquid yielded 43.5

(74% theory) of 2,4-diphenyl-4-methyl-2-pentene^*^, b.p. 12&-129 °

1-2 mm. ), nj^ 1.5654, and some polymeric material

Anal. Calcd. for C^gHgQ: C, 91.5; H, 8.50.

Found1 1 :

C, 91.5; H, 8.77. Summary 1.

Organometallic derivatives of styrenes have been

prepared by the reactions of nuclearly halogenated styrenes with magnesium or lithium.

The metallation reactions are

accompanied by large amounts of polymerization. 2.

The above organometallic compounds have been employed

like typical Grignard reagents in the synthesis of sub­ stituted styrenes.

The yields of the desired products are

low because of polymer formation. Lafayette, Indiana

(Contribution from the Purdue Research Foundation and the Department of Chemistry, Purdue University)

Monomers and Polymers, VIII• THIOSTYRENES 1

1 From the Ph. D. thesis of C.


. Carlson, Purdue University

By Gr. Bryant Bachman and C. L. Carlson


No previous investigators have reported the synthesis and polymerization of monomeric styrenes and ct-methy 1 styrenes containing sulfide and sulfone groups substituted on the aromatic nucletfs.

We have undertaken the preparation of

some typical examples of these compounds in order to observe their polymerization behavior.

The compounds prepared are:

p-(methylmercapto-) styrene, p- (methylsulfonyl) styrene, p-methylmercapto-o(-methylstyrene, and p-ethylmercaptoo(-methylstyrene.

The synthetic scheme employed is out­

lined below. COGH,5 (CH3 CO)gO

coch 3 KMnÛ4





hc=ch 2




GH 3-Ç-GH 2







RS0 2 IX





The position occupied by the acetyl group in IX was confirmed by performing a haloform reaction with II and comparing the melting point of the acid product with that of p-methylmercaptobenzoic acid as reported by Gattermann' 2 Gattermann, Ann., 595. 226 (1912) It is interesting to note that VII, because of its almost complete insolubility in ether, failed to react with méthylmagnésium iodide. directly, failed.

All attempts to dehydrâte VII I ,

This compound was converted to the

corresponding bromide which was dehydrobrominated success­ fully. An alternative approach to the synthesis of sulfurcontaining styrenes is outlined below. SH



(CH3 )£S04 NaOH


BOB I 3 AI 2 O 3



Since the Grignard synthesis to introduce the mercapto group 3 3 Taboury, Oompt. rend., 138, 982 (1904) gave yields of only 11 %, and since p-bromophenyl methyl sulfide 4 4 Taboury, Bull. soc. chim., (3) 31 1185


was found to react sluggishly toward magnesium, this synthesis is less satisfactory than the one previously outlined.

None of the styrenes were prepared by this method»

An attempt was made to prepare p-mercaptostyrene via p-mercaptoacetophenone.

However, we were unable to obtain

the latter compound by acetylating thiophenol under FriedelCraf ts conditions.

More than 20 experiments were run using

various temperatures (0-150°), solvents (CSg, C 5H 5NO 2 , petroleum ether), catalysts (AICI 3 , B F 3 , SnCl^) , ratios of reactants, and orders of addition of the reactants. Phenyl thioacetate was formed quite readily, but no other reaction occurred unless the temperature was raised to 150° or higher, at which point only tars were formed.

From these

none of the desired product could be isolated. The above resistance of thiophenols to nuclear acetyation has not been adequately emphasized in the chemical literature5, 5 Thomas, MAnhydrous aluminum chloride in organic chemistry” , Reinhold Publishing Co., New York, N. Y . , 1941, page 369. although it has been reported by Auwers and Arndt 5 6 Auwers and Arndt, Ber., 42, 537 (1909)

that p-thiocresol does not undergo a ketone synthesis when subjected to the usual Friedel-Crafts conditions. 7 Kastner, Thesis, Marburg, 1937;

Kastner 7

"Newer Methods of Prep­

arative Organic Chenistry? Interscience, New York, 1948, page 281.


has pointed out that the nuclear acétylation of phenyl esters by boron fluoride catalysts is more dificult than the reaction with phenols and phenyl ethers.

Similarly, phenyl thio-

esters would be expected to be more resistant to acétylation than the corresponding thiophenols.

However, the great

resistance of the esters here encountered was unexpected. The simplest way to account for this deactivation of the nucleus would be to assume that the mercapto group is con­ verted to an electron-withdrawing group capable of de­ activating the nucleds sufficiently to prevent its reaction with acylating agents.

A possible mechanism for this might

be SH

+ S( C0CH3 )2


CH 3 COCI xruTs— -

+ CH 3 CO 2H HCl ■►A1(0H)3

It is difficult, however, to understand why the alkyl mercapto benzenes should not behave similarly to thiophenol. Actually methylmercaptobenzene acetylates readily in 87% yield under mildest conditions. In a final attempt to obtain the desired acetylated product, diphenyl disulfide was treated with acetyl chloride and AlClg in carbon disulfide solution.

The products of

this reaction were resinous materials and a small amount of thiophenol. p-(Methylmercapto)styrene was polymerized satisfactorily by both the emulsion and solvent techniques, and copolymer-


ized with butadiene in an emulsion system.

The two o(-methyl-

styrenes formed rubbery copolymers with butadiene.

In benzene

solution p-(methylsulfonyl)styrene polymerized to a viscous oil only. Acknowledgement. The authors are indebted to the General Tire and Rubber Company and the Purdue Research Foundation for support in the form of a fellowship. Experimental n-(Methylmercapto)acetophenone. Acetic anhydride, 65.0 g. (0.64 mole), was added dropwise to a mixture of methyl phenyl sulfide, 98.5 g. (0.8 mole), aluminum chloride, 240 g. (1.8 mole), and 340 ml. of carbon disulfide.

The mixture

was stirred and heated on a steam cone for two hours, after which time the evolution of hydrogen chloride had slackened.

Distillation of the carbon disulfide followed by

hydrolysis of the residue with dilute hydrochloric acid gave 92 g. (87% theory) of a yellow crystalline product, m.p. 82-83° (from petroleum ether).

Upon vacuum sublimation

the product was white. Anal. Calcd. for CgHiQOS: C, 65.2; H, 6.03.


C, 65.4; H, 6.16. 8 Carbon and hydrogen analyses by Dr. H. Galbraith, Purdue

University. p-(Ethylmercapto)acetophenone^ 9 Auwers and Berger, Ber., 27, 1738 (1894)


was prepared by a similar procedure. of ethyl phenyl sulfide and 63 g.

From 106 g. (0.77 mole)

(0.62 mole) of acetic

anhydride, 60 g. (53 % theory) of the ketone was obtained. p-Methylmercapto-oC-methylstyrene. A solution of p-(methylmercapto)acetophenone, 50 g. (0.3 mole), in 200 ml. of ether was added to a solution of méthylmagnésium iodide prepared from methyl iodide, 50 g. (0.35 mole), 8.4 g. of magnesium, and 200 ml. of ether.

The mixture was refluxed

§ hour and hydrolyzed with saturated aqueous ammonium chloride solution.

Evaporation of the ether yielded a yellow solid,

presumably the tertiary alcohol.

This solid was refluxed

with 10 g. of fused potassium bisulfate at 100 mm. for 20 minutes, and then distilled, b.p. 85° (1-2 mm.), m.p. 51°, yield 20 g. (41% theory). Anal. Calcd. for C1 oII12S:

73.2; H, 7.32.

Found8 :

C, 73.6; H, 7.17. p-(Ethylmercapto)-o&methylstyrene was prepared by this same procedure.

From p-(ethylmercapto)acetophenone, 59.5 g.

(0.33 mole), 19 g. (31% theory) of the styrene was obtained, b.p. 94-96° (3-4 mm.), m . p . 29-30°. Anal. Calcd. for

C , 74.1; H, 7.86. Found®:

C, 73.95; H, 7.73. 1-(p-Methylmercaptophenyl)ethanol. A solution contain­ ing p-(methylmercapto)acetophenone, 16.6 g . (0.1 mole), aluminum isopropoxide, 20 g. (0.1 mole), and 100 ml. of isopropyl alcohol was distilled at the rate of 10 drops per minute for 6 hours.

An additional 75 ml. of isopropyl


alcohol was added during the distillation*

The excess

isopropyl alcohol was removed under reduced pressure, and the residual oil poured into a solution of 35 ml. of hydrochloric acid in 175 ml* of water. was taken up in ether and dried.

The organic layer

Evaporation of the ether

yielded a brown oil which crystallized on cooling in an ice bath.

Recrystallization from petroleum ether gave 14 g.

(83% Yield) of white crystals, m.p. 38-40°. Anal. Calcd. for CgH^gOS: C , 64.3; H, 7.14.

Found8 :

C, 64.3; H, 7.35. p-(Methylmercapto)styrene. A solution of 60 g. (0.36 mol e ) of 1-(p-methylmeroaptophenyl)ethanol in 75 ml. of benzene was allowed to drop slowly (3 hours) into a vertical column packed with aluminum oxide.

The temperature of the

column was maintained between 300 and 3 2 5 and the pressure was approximately 30 mm.

The benzene solution of the product

was condensed in a series of dry-ice traps, dried, and distilled.

The product was a colorless liquid, b.p. 83-85°

(3 mm.), n|° 1.6186, d |5 1.0384, yield 29 g. (54% theory). Anal. Calcd. for CgH^oS: C, 72.0; H, 6.67.

Found8 :

C, 72.0; H, 6 .95o p-(Methylsulfonyl)acetophenone. A solution of 20 g. (0.12 mole) of p-(methylmercapto)acetophenone in 50 ml. of glacial acetic acid was heated to 40°.

A solution of

potassium permanganate, 26 g . , in 600 ml. of water was added and the temperature rose to 60-70°.


xv i

ml. of water were added, and the solution was allowed to stand until it reached room temperature.

Small portions of a

saturated solution of sodium sulfite were added to remove the excess permanganate. and filtered.

The solution was cooled to 10°

Yield 22.8 g. (95% theory) of white crystals,

m.p. 127-128°(from 95% ethanol). Anal. Calcd. for Cgïï^QOgS: C, 54.6; H, 5.21.

Found8 :

G, 54.6; H, 5.05. l-(p-Methylsulfonylphenyl)ethanol. A solution contain­ ing p-(methylsulfonyl)acetophenone, 19.8 g. (0.1 mole), Aluminum isopropoxide, 20 g. (0.1 mole), and 150 ml. of isopropyl alcohol was distilled at a rate of 10 drops per minute for two hours.

The excess isopropyl alcohol was

removed under reduced pressure, and the residual oil poured into dilute hydrochloric acid.

Some resinous material was

filtered, and the solution was extracted 4 to 6 times with 150 ml. portions of ether.

Evaporation of the ether

yielded 14 g. (71% theory) of white crystals, m . p . 95-96° (from 95% ethanol)• Anal. Calcd. for CgH^gOgS: C , 54.1; H, 6.00.

Found8 :

C, 54.4; H, 5.94. 1 - (p-Methylsulfonylphenyl)ethyl bromide. The above alcohol, 25 g. (0.125 mole), was dissolved in a ten-fold excess of 48% hydrobromic acid.

The solution was allowed

to stand for two days, during which time a white crystalline solid was formed.

This solid was filtered, washed with water,


and dried in a vacuum desiccator, m.p. 87-88° (from petroleum ether), yield 22 g. (66% theory). Anal. Calcd. for GgH^iBrOgS: C, 41.1; H, 4.18.

Found8 :

C, 41.4; H, 4.48. p-(Methylsulfonyl)styrene. Twenty-two g.

(0.084 mole)

of the secondary bromide described above were dissolved in 200 ml. of absolute ethanol containing a two-fold excess of potassium hydroxide.

The solution was refluxed for one

hour, cooled, and filtered. volume and taken up in ether. dried, and distilled.

It was evaporated to a small The ether solution was filtered,

A fraction

was collected from 148-150°

(4 mm.), m.p. 37-38°, yield 6 g. (40% theory). Anal. Calcd. for C 9H 10 O 2 S: C , 59.4; H, 5.49.

Found8 :

C, 59.2; H, 5.73. Preparation of Polymers and Copolymers. Polymers of p-(methylmercapto)styrene and p-(methylsulfonyl)styrene were prepared by heating a 10% solution of the monomers in benzene at 75-80° for several hours, using 1% benzoyl peroxide as catalyst.

Copolymers of the four new monomers

with butadiene were made at 40° in sealed pyrex tubes, using the following formula, butadiene 7.5 parts, substituted styrene or

methylstyrene 2.5 parts, water 20 parts, soap

0.5 part, potassium persulfate 0.3 part, and dodecyl mercaptan 0.06 part,

p-(Methylsulfonyl)styrene did not

form a copolymer with butadiene since most of the monomer was recovered unchanged.

The other three monomers co­

polymerized readily with butadiene.


Summary 1.

The syntheses of four new styrenes and o(-methy1 styrenes

with sulfide and sulfone groups substituted on the aromatic nucleas are described. 2.

It has been found that the sulfide group permits free-

radical- catalyzed polymerization and copolymerization, however, p-(methylsulfonyl)styrene yields only viscous oils under the same conditions under which p-(methylmercaptojstyrene gives a crumbly polymer. Lafayette, Indiana


Abstract of Section III A step in the proposed synthesis of p-mercaptostyrene involved the Friedel-Crafts acétylation of thiophenol. Since this reaction has never been reported, an investigation was made to determine the feasibility of preparing p-mercaptoacetophenone by this method.

Attempts were made to bring

about this reaction under a variety of conditions which included the use of three solvents, three catalysts, selected to cover a broad range of activity, and two aoetylating agents. Solvents. ether were used.

Carbon disulfide, nitrobenzene, and petroleum These represent solvents which are commonly

used in Friedel-Crafts reactions. Catalysts.

The three catalysts represent varying

degrees of activity.

Aluminum chloride, because of its

well-known catalytic activity, was used in the majority of the experiments, but runs were also made using boron fluoride, which is mildly catalytic, and stannic chloride, which is of intermediate activity. Aoetylating Agents.

Both acetic anhydride and acetyl

chloride were used either in molar quantities or in molar excess.

Every possible order of mixing the reagents was

tried, and the reaction was carried out at room temperature and at higher temperatures. Under every set of experimental conditions which were investigated, the only product obtained was phenyl thioacetate.


Acétylation was found to occur only on the sulfur atom, and at no other point in the molecule.

Even when two molecular

portions of the aoetylating agent were used, the thioester was the only product isolated.

Attempts to ring-acetylate

phenyl thioacetate resulted in the recovery of the thioester. Since it was not found feasible to prefare p-mercaptoacetophenone, a practical laboratory synthesis of p-mercaptostyrene was not developed.


Introduction One difficulty in the manufacture of GR-S type syn­ thetic rubber is the ease with which styrene will undergo polymerization during storage.

This polymerization during

storage is prevented by the use of polymerization inhibitors which must subsequently be removed before copolymerization with butadiene will take place. It has been known for some time that, while o(-methylstyrene undergoes homopolymerization only with difficulty, it will copolymerize readily with butadiene.

Its lack of

tendency to polymerize alone gives oC-methylstyrene an ad­ vantage over styrene in that no inhibitors need be added during storage, thus eliminating the inhibitor-removal step prior to use.

It would seem a worthwhile research program,

therefore, to prepare a variety of substituted cC-methylstyrenes in order to test their usefulness as substitutes for styrene in GR-S type polymers. A considerable number of substituted ofc-methylstyrenes has been prepared and tested at Purdue University.


synthetic methods employed in preparing these monomers are outlined in figure 1.

Methods I and II are limited

to intermediates which contain no other groups affected by Grignard reagents.

Method III, recently reported by

Bachman and Heilman^-, ,is widely applicable. It was hoped, as a result of the work reported herein, to develop a general laboratory synthesis for a wide variety

2 OH CH 3 -C-CH 3


ô X


CH 3 -CzCH 2

0 —-Ô X

OH ch 3 -c-ch3

co 2 c 2h 5

oh 3 -c=ch 2

Ô —- Ô


gh 3 -gh-gh2oi





gh 3 -c=ch 2



Fig. 1 Some Syntheses of Substituted o^-Methylstyrenes.

of substituted ot*methylstyrenes.

The proposed synthesis

was to involve a single type of intermediate, namely, a nuclearly halogenated o^methylstyrene. The purpose of this work was to determine to what extent organometallic compounds such as p-isopropenylphenylmagnesium bromide (A), and p-isopropenylphenyllithium (B) might be used to prepare substituted o^methylstyrenes.

To this end, a study was made of the reaction

between the metals, magnesium and lithium, and the halides m- and

p-bromo, and p-iodo-o^methylstyrenes.




CH 3 -C-CH 2 L



( A)

Through these organometallic compounds a large number of substituted oC-methylstyrenes could be readily prepared. Figure 2 gives examples of the types of reaction which could be carried out.

A large number of other compounds

CH3-C=CH 2




CH 8 -CH2 0H Fig. 2




Proposed Syntheses of New Substituted o^-Methylstyrenes.

which react with organometallic compounds could also be used. In the course of this investigation it was found that dimerization or polymerization occurs at the unsaturated linkage in ^-methylstyrenes during the formation of the organometallic compound.

As a result of this reaction,

p-isopropenylbenzoic acid, formed by carbonating the

the organometallic solution, was obtained only in low yields.

It was met found possible to isolate neutral

products from the reaction mixture.

Preparation of Intermediates The p-bromo-ofc-methylstyrene2 used in this work was prepared by two different methods as shown below. CH 3


1 Cy y x




CO 2 G 2H 5



h 2 so 4

r Cy V X



OH gh3 - c - oh3

(1 )

2 CHsM g I

(3 )



gh5 - c =ch2

(C H 5 C 0 )20





OH CH3 -C *C H 3

GH3 -GzGHg


(CH5 ) 2 C0



Br (2 )




(CH3C 0 ) 20

Reflux Br


Each of these methods has certain advantages.


method indicated under (1 ) contains more steps, and also, the operations involved in carrying out this synthesis are

more time-consuming than is the case with synthesis (2 ). Synthesis (2 ) has one disadvantage which, however, was not considered serious in this work, since the chief objective in this work was the development of the synthesis of substituted oC-methylstyrenes rather than to prepare the polymers formed by them,

it is possible in the reaction

with magnesium that a trace of di-Grignard reagent might be formed.

If this were the case, then some of the final

product might contain a trace of p-diisopropenylbenzene. This divinyl compound would be an undesirable impurity in a monomer to be used for polymerization work since it would be capable of forming cross links in the polymer.


cross-linked polymer would have properties very different from those of the polymer formed from the pure monomer.



view of the work of Gilman, Beaber, and Jones

, however,

it seems unlikely that any appreciable amount of the diGrignard reagent would form.

These workers report that

under ordinary conditions there is no evidence of the form­ ation of the di-Grignard reagent from p-dibromobenzene when no catalyst is used.

The first sample of p-bromo-cC-

methylstyrene prepared for this work was made by method (1 ). Since this method was too time-consuming, subsequent samples were made by method (2 ). m-Bromo-c^-methylstyrene

was prepared by reacting

methyl m-bromobenzoate with two molecular portions of méthylmagnésium iodide, and dehydrating the resulting tertiary alcohol.

OH CH 3 -Ç-CH 3



(1) 2 CH^lgl

Br (2) H +


CHs-ÇrCHg (CH 3 C 0 )go

/ X Br

p-Iodo-o^-methylstyrene, which has not previously been reported in the literature, was prepared by a synthesis analogous to method (1 ) under the discussion of p-bromo - 06 methylstyrene.

Discussion Very early in the work it became evident that these halogen compounds were extremely sluggish in their behavior toward magnesium.

For example, the para-bromo compound,

which was used in the major portion of the work resisted all attempts to form the Grignard reagent in any appreciable yield.

Indeed, the only indication of any reaction at all

was obtained with specially-prepared activated magnesium^. Even in this case the yield of organometallic compound obtained after 24 hours was negligible, since practically all of the magnesium was recovered.

All attempts to form

this Grignard reagent by using (1) a crystal of iodine as an initiator,

(2 ) a cohalide as an initiator, or (3)

n-butyl ether as a solvent for the reaction were even less successful since no positive indication of the formation of the desired Grignard reagent was observed under these conditions. The reaction of these halides with metallic lithium appeared to be more promising.

In the case of p-bromo-ofc-

methylstyrene it was necessary to add a cohalide, methyl iodide, in order to initiate the formation of the organo­ metallic compound.

Invariably a negative Gilman test5 was

observed after an ether solution of p-bromo-oG-methylstyrene was refluxed for several hours with metallic lithium without the addition of a cohalide.

In the case of p-iodo-ofc-methyl-

styrene, however, the reaction began after a few minutes

refluxing without the addition of methyl iodide.


formation of this organometallic compound was accompanied by the appearance of a dark-red color.

Carbonation of

the organometallic compounds and subsequent isolation of the product, p-isopropenylbenzoic acid, led to a 10 % yield in the case of the bromo compound, and a 19% yield in the case of the iodo compound.

Hydrolysis of the organometallic

solution, and titration of the resulting mixture with standard acid indicated the formation of organometallic derivatives in as high as 64% Yields.

In all cases a considerable

amount of polymeric material was formed.

The isolation of

p-isopropenylbenzoic acid gave an indication that the desired organometallic compound could be formed,

though in low yield.

Since the desired organometallic compound was known to form, it seemed advisable to react it with a carbonyl com­ pound in order to determine the feasibility of isolating a neutral compound from the reaction mixture.


and acetaldehyde were chosen for this purpose.

In both

cases the product obtained after hydrolysis and evaporation of the ether was a red-brown gummy material.

Attempts to

isolate the product from this material by vacuum distillation and solvent extraction were not successful.

When a portion

of the gummy material was heated under a pressure of 1-2 mm. , it gradually became fluid.

Continued heating resulted only

in decomposition and discoloration of the material. distillate was obtained.


The material could be dissolved

in such solvents as alcohol and acetone, but no solid material could be obtained upon cooling.

Evaporation of

part of the solvent yielded the original gummy material. Petroleum ether dissolved only a small amount of the material which was reprecipitated when the solution was cooled. The occurrence of polymeric material in every case in which p-isopropenylphenyllithium was prepared led to speculation as to its mechanism of formation and structure. Staudinger and

Breuscb? have found that ^-methylstyrene

reacts in the presence of sulfuric acid to form dimers and low molecular weight polymers containing up to 8 units of the monomer.

He- hao isolated these polymers and determined

their physical properties.

Since at no time during the

formation of p-isopropenylphenyllithium, during subsequent reactions, or during attempted isolation of the reaction product did the reaction mixture come into contact with strong acid, it seems obvious that acid-catalyzed poly­ merization can not account for the formation of the polymer. Though free radical-catalyzed polymerization of o(rmethyl­ styrene, alone, is known to proceed only with difficulty, free radical-catalyzed copolymerization with butadiene is known to take place readily.

Since the formation of an

organometallic compound by the direct action of a halide on an active metal is known to proceed by a free-radical mechanism, it seems possible that the free radicals produced in the reaction might bring about polymerization or dimer-

ization of the substituted 06-methy 1 styrene.

While oC-wethyl-

styrene, alone, does not readily undergo free-radioalcatalyzed polymerization, it should be pointed out that in the formation of the organometallic compound molar quantities, rather than catalytic quantities, of free radicals are involved, and that these larger quantities might be expected to effect a proportionally larger amount of polymerization. In studying the effect of free radicals, resulting from the formation of an organometallic compound, upon the un­ saturated linkage in oC-methylstryrene, it seemed desirable to use o(-methylstyrene, itself, rather than one of the halogen-substituted compounds which were used in the greater portion of this work.

This choice greatly simplifies the

number of possible reaction products.

It is to be noted

also that the polymers of ^-methylstyrene containing up to 8 units of the monomer have been reported by Staudinger and Breusch , whereas the corresponding polymers of the halogen-substituted ot-methylstyrenes have not been reported. If a low molecular-weight polymer of c^-methylstyrene were obtained as a product, it could be identified by comparison with known compounds.

Thus the identification of products

would be simplified. It was decided to determine the effect of the formation of an organometallic compound upon the unsaturated linkage of ct-methylstyrene in an experiment

which was carried out

in the following way.

A solution of methyl iodide in ether

was added to a flask containing magnesium and a solution of c3


Since the first step in the reaction with thiophenol is thioester formation, it might be expected by analogy with the phenyl esters, that the phenyl thioesters would undergo ring acétylation only with difficulty. The experimental conditions used varied over a consider­ able range.

Three different solvents were used, carbon di­

sulfide, nitrobenzene, and petroleum ether.

These represent

the solvents most commonly used in Friedel-Crafts reactions. When stannic chloride was employed as the catalyst, no solvent

was used. The three catalysts used were selected to cover a broad range of activity in Friedel-Crafts type reactions. Aluminum chloride, because of its well-known catalytic activity, was used in the majority of experiments, but runs were also made using boron fluoride, which is known to be catalytic, and stannic chloride which is of intermediate activity^. Both acetic anhydride and acetyl chloride were used as acetylating agents under various conditions.


possible order of mixing the reactants was tried, and the reaction was carried out at room temperature, and at higher temperatures, but the resulting product was always the thioester even when a considerable excess of acetylating agent was used. Since it was not found feasible to prepare p-mercaptoacetophenone, a practical laboratory synthesis of p-mercaptostyrene was not developed.

Expermental Some typical experiments will be described in detail in order to present a clearer picture of the extent of the work carried out. .Reactions using petroleum ether as the solvent.

(1 )

Acetic anhydride, 25.5 g. (0.25 mole), was added to a stirred mixture of thiophenol, 27.5 g. (0.25 mole), aluminum chloride, 100-133 g. (0.75-1.0 mole), and 150 ml. of petroleum ether. The mixture was cooled in an ice bath during the addition, and then allowed to warm up to room temperature.


about one hour the reaction mixture had turned dark red, and consisted of a gummy complex layer covered by petroleum ether.

The mixture was allowed to stand for 24 hours at

room temperature, and was then hydrolyzed by the addition of cold, dilute hydrochloric acid.

The organic layer was dried

and distilled.

A fraction was collected from 70-74° (3-4 mm) 20 weighing 27.5 g . ; n^ 1.5700. This refractive index agrees with that reported for the phenyl ester of thioacetic acid: 20 36 np 1.5706 . This product failed to give a positive test for a carbonyl group when treated with 2 ,4-dinitrophenylhydrazine.

It would not dissolve in 5% sodium hydroxide solution. (2 )

Using the same proportions of reagents as in the

above experiment, two more runs were carried out using petroleum ether as the solvent.

In one case the thiophenol was added

to a cooled, stirred mixture of the other reactants.


stirred mixture was heated to the reflux temperature of the

petroleum ether for about one hour and then was allowed to stand for about 24 hours.

The reaction mixture was hydrolyzed

and worked up in the same manner as before.

About 25 g. of

phenyl thioacetate was obtained as the product. (3)

This experiment was carried out exactly as described

in (2 ) except that the aluminum chloride was added to a mixture of the other three reagents.

In this case, as before,

about 25 g. of phenyl thioacetate was obtained.


represents a yield of about 71%. Reactions using nitrobenzene as the solvent. (1 ) Thiophenyl, 20 g. (0.18 mole), was dissolved in 150 ml. of nitrobenzene, and to this solution was added 32 g. (0.4 mol e ) ; of acetyl chloride.

Aluminum chloride, 105 g. (0.8 mole),

was then added slowly with stirring.

The mixture was then

heated on a steam cone for about six hours and then allowed to stand for 18 hours.

The reaction mixture was hydrolyzed

by means of dilute hydrochloric acid, and then steam distilled.

The residue from the steam distillation was

extracted with ether, and the ether evaporated.

The residue

obtained weighed less than one gram and reacted negatively toward 2 ,4-dinitrophenylhydrazine reagent.

The steam-volitile

fraction also gave a negative indication of a carbonyl group. (2)

A mixture containing 30.4 g. (0.2 mole) of phenyl

thioacetate, 15.6 g. (0.2 mole) of acetyl chloride, and 133 g. (1.0 mole) of aluminum chloride in 150 ml. of nitro­ benzene was slowly heated to 150° with stirring.


approximately this temperature the mixture turned dark,

and reacted vigorously, although no hydrogen chloride was evolved.

Carbonization appeared

to be complete, and the

contents of the flask were fused to a solid mass of black tarry material.

It seems possible that at this temperature

the sulfur compound might have been oxidized by the nitro­ benzene. Reactions using carbon disulfide as the solvent. (1) A mixture of phenyl thioacetate, 53 g . (0.32 mole), aluminum chloride, 1.40 g. (1.05 mole), and carbon disulfide, 200 ml., was prepared, and to this mixture was added 40 g. (0.5 mole) of acetyl chloride.

The reaction mixture was stirred at the

reflux temperature overnight, and hydrolyzed by means of dilute hydrochloric acid. and taken up in ether.

The organic layer was separated

The ether solution was dried and

distilled yielding the starting material, phenyl thioacetate. (2) This run was similar to (1) except that thiophenol was used instead of the thioester.

Two molecular portions

of acetyl chloride were used for acétylation.

The product

isolated from this run was phenyl thioacetate. (3) A solution of thiophenol, 27.5 g. (0.25 mole), in 100 ml. of carbon disulfide was saturated with boron fluoride.

Acetyl chloride, 39 g. (0.5 mole), was added, and boron fluoride was again passed into the solution.

Since there was no

apparent reaction on standing, the mixture was warmed on a steam cone for one hour, and again saturated with boron fluoride. The mixture was allowed to stand, and was then warmed all of the boron fluoride was driven off.


When the reaction

mixture was hydrolyzed, and worked up in the usual manner, phenyl thioacetate was obtained in almost quantitative yield. (4) Attempted acétylation of diphenyl disulfide. Diphenyl disulfide, 11 g. (0.05 mole), was added to a mixture containing acetyl chloride, 7.8 g. (0.1 mole), and aluminum chloride, 66 g. (0.5 mole), in 75 ml. of carbon disulfide. The mixture turned black almost immediately. to stand at room temperature overnight.

It was allowed

Hydrolysis with

dilute hydrochloric acid followed by steam distillation of the resulting mixture gave a small amount of thiophenol.


organic residue from the steam distillation contained a brown resinous material which gave no indication of a carbonyl group when tested with 2 ,4-dinitrophenylhydrazine reagent. No solvent - stannic chloride catalyst. (1) Acetyl chloride, 40 g. (0.5 mole), was added to 160 g. (0.61 m ole ) of stannic chloride. addition. thiophenol.

No heat effect was noted during the

To this mixture was added 27.5 g. (0.25 mole) of The reaction mixture gradually turned dark red

as it was stirred and heated on a steam cone for two hours. Hydrolysis was accomplished by pouring the mixture onto ice and hydrochloric acid.

Steam distillation of this mixture

yielded a small fraction of thiophenol, less than 5 g ., and a larger amount of non-volitile resinous material. (2)

A mixture of phenyl thioacetate, 38 g. (0.25 mole),

acetyl chloride, 19.5 g. (0.25 mole), and stannic chloride, 160 g. (0.61 mole), was allowed to stand at room temperature for about 20 hours.

When the mixture was hydrolyzed and

stream distilled in the same manner as above, most of the phenyl thioacetate was recovered along with a small amount of resinous material.


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Summary !•

Organometallic derivatives of styrenes have been

prepared by the reactions of styrenes with magnesium or

nuclearly halogenated o(^methyllithium.

The metallation reactions

are accompanied by large amounts of polymerization. 2.

The above organometallic compounds have been employed

like typical Grignard reagents in the synthesis of sub­ stituted o(rmethylstyrenes.

The yields of the desired products

are low because of polymer formation. 3.

The syntheses of four new styrenes and o(rmethylstyrenes

with sulfide and sulfone groups substituted on the aromatic nuoleas are described. 4.

It has been found that the sulfide group permits free

radical catalyzed polymerization and copolymerization, however, p-(methylsulfonylstyrene yields only viscous oils under the same conditions under which p-(methylmercapto)styrene gives a crumbly polymer. 5.

It has been found that thiophenol has an unexpected

resistance to Friedel-Crafts acylation.

VITA Carl L. Carlson was born on January 30, 1924 in Lincoln, Nebraska.

He received his elementary education

in the public schools of Lincoln, Nebraska, and was grad­ uated from Lincoln High School in January, 1942.

He then

entered the University of Nebraska and received the B. S. Ch. E. degree in January, 1946, and the M. A. degree in August, 1947.

In September, 1947 he entered Purdue

University and began work on a fellowship sponsored by the General Tire & Rubber Company the following June.

He retained

this position until June, 1950, when his work for the degree of Doctor of Philosophy was completed. Phi Lambda Upsilon and Sigma XI.

He is a member of