Hofmann degradation studies related to cyclocctatetraene

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NAME AND AD DRE SS

DATE

NORTHWESTERN UNIVERSITY

HOFMANN DEGRADATION STUDIES RELATED TO CYCLOOCTATETRASNE

A DISSERTATION SUBMITTED TO THE GRADUATE SCHOOL IN PARTIAL FULFILLMENT OF THE REQUIREMENTS

for the degree DOCTOR OF PHILOSOPHY

DEPARTMENT OF CHEMISTRY

BY ELWOOD HENDERSON ENSCR EVANSTONj ILLINOIS JUNE*19^2

ProQuest Number: 10101369

All rights re s e rv e d INFORMATION TO ALL USERS The quality o f this r e p r o d u c tio n is d e p e n d e n t u p o n t h e quality o f t h e c o p y sub m itte d . In t h e unlikely e v e n t t h a t t h e a u th o r did n o t s e n d a c o m p l e t e m anuscript a n d t h e r e a r e missing p a g e s , t h e s e will b e n o t e d . Also, if m aterial h a d to b e r e m o v e d , a n o t e will i n d ic a te t h e de le tio n .

uest P roQ uest 10101369 Published by P ro Q u e st LLC (2016). C opyright o f t h e Dissertation is held by t h e Author. All rights rese rv ed . This work is p r o t e c t e d a g a in s t u n a u th o rize d c o p y in g u n d e r Title 17, United S tates C o d e Microform Edition © ProQ uest LLC. P ro Q u e st LLC. 789 East Eisenhow er Parkway P.O. Box 1346 Ann Arbor, Ml 48106 - 1346

ACKNOWLEDGMENT

The author wishes to take this opportunity to express his thanks and appreciation to Professor Charles D« Hurd whose helpful suggestions, broad experience, and sound judge­ ment were invaluable throughout the course of this investigation.

TABLE OF CONTENTS Paget

acknowledgment :

I.

INTRODUCTION A.

Historical Background I. Willstatter*8 Synthesis of Cyclooctatetraene. • • • 1 2.

Table I .................

2

5*

Linstead's Repetition of Willstatter*e Synthesis • • 5

4.

Goldwasser and Taylor's Attempt to Synthesize

Cyclooctatetraene • • . • • . . . . . . . . . . • . . 4

B*

5.

Vincent's Attempt to Synthesize Cyclooctatetraene • . 4

6.

Kohler's Attempt to Synthesize Cyclooctatetraene

7.

Steadman's Attempt to Synthesize Cyclooctatetraene . 5

3.

Synthesis of a Substituted Cyclooctatetraene • • • • 6

9*

Fry and Fieser's Benzocyolooctans . . . . . .

. . .7

10.

Attempted Syntheses l,2-5,4-Dibenzo-l,5#5,7Cyclooctatetraene..............

....3

• 5

11.

Anamolous Hofmann Degradations

............ 10

12.

The Hofmann Degradations of Hurd and Drake. • . . • 15

Discussion of the Aims and Results of the Problem 1. Proposed Synthesis of Pentenyltrimethylammonium Hydroxide 2.

l4

Synthesis of 5~P©ntene-2-ol..................... 15 Dipentenyl ether . . • • • •

«•••.

......... 16

4.

4-Bromo-2-pentene......................... . . 1 6

5*

Pentenyltrimethyl ammonium Bromide

........ .17

6. Absorption of 1,5-Psutadiene by Maleic Anhydride 7.

Analytical Distillation Method of Analysis

• 18

. . . . 19

8. Hofmann Degradation of Pentenyltrimethy1ammoniumHydroxide . . . . . . . . . . . . . ............. 20 9* Preparation of the Mono and Di Trimethylammonium Salts Salts of l,4-Dichloro-2-butene • a. b.

Hofmann Degradation of the Mono Salt Hofmann Degradation of the Di Salt

......... 21 • • • • 21 . . . . 22

10.

Proposed Synthesis of Cyclooctatetraene

.......

11.

High Dilution Condensations of Crotonaldehyde

25

• . 25

Page

II. EXPERIMENTAL A* Preparation of the Bromomagnesium Salt of 5-Pentene-2-ol • * ♦ • • • * . • • • • * * • * • • * «

28

I.

Isolation of 5“P®ntene-2-ol by Extraction • • . . 28

2*

Isolation of 5'“P®ntene-2-ol bySteam Distillation* 29

B.

Formation of 4-Bromo-2-pentene . . . • • • .......... 29

0*

Preparation of Trimethyl amine

D*

Reaction of 4-Bromo-2-pentene with Trimothylamine

• . . . .............. 50

1* Using No Solvent . • • . • • • • • • • • 2* E.

.......

30

Using Dioxane as Solvent................... 51

Reaction of 4-Bromo-2-pentene with Other Amines

F.

1*

With Pyridine.........................

2*

With Morpholine

5*

With Dimethylaniline

. . . 51

......... 52 . . . . . . . . . . . . . .

52

Reactions in which l,5"*P®ntadiene was Formed as a By-product

G.

1.

From a Grignard Reaction....................... 52

2.

From the Splitting of Dipentenyl Ether • • • • » • 55

Establishment of Methods of Analyzing Pentadiene Mixtures 1. Figure 1

54a

2* Analytical Distillation • • • • • • . • • * • • • 5 4 5. Figure 2 ...................... ............ 55a 4*

Analysis with an Orsat Apparatus

••••••••

55

5. Table I I ................................... 56a 6* Table I I I .................................. 56a 7. Table 17 8 . Table 7

. * ...............................57a ................................ 57

H.

Physical Properties of Pure l,5”P®ntadiene .......

58

I*

Dispersion Scale Reading of l,5“P®ntadiene .......

58

. 1* Table 7 1 .................................. 59 J*

Formation and Pyrolysis of Pentenyltrimethylammonium Hydroxide • • • • • • • • • • • • • • • • •

59

K*

Figure 5 * • • • • • •

• . . . . . . . . . . . . . .

40a

L.

Analysis of the Product of Pyrolysis • • • • • . • •

40

M.

Preparation of the Mono Salt of l,4-Dichloro-2butene ♦ • • • • • • • • • • . . . . ♦ . . . . . . .

N* 0.

4l

Preparation of the Di Salt of l,4-Dichloro-2butene • • • * • • * • • * • • ♦ . . . • .........

4l

Hofmann Degradation of the Mono S a l t ..........

42

Pago

III. 17* V.

P*

Analysis of the Pyrolysis Produots........ .

Q. R.

Table 7 1 1 ....... * ♦ . * ♦ ...................44a Table 7III . * . ............................ 44a

S,

Hofmann Degradation of the Di Salt

T*

Analysis of the Products of Pyrolysis

U.

Figure 4

V.

Description of the High Dilution Apparatus • • • • . 45

W*

Condensations of Crotonaldehyde Using 0.5Mole

2.

Using MolarAmounts

BIBLIOGRAPHY

. • • • • • » *44 44

♦ ...................... 45a

1.

SUMMARY .. . .

4^

ofSodium Methoxide........... 46 ofSodium Methoxide ♦ • • .

...................................

47 46

............................ 49

Y I T A .............. * ................................ 51

INTRODUCTION Historical Background Ons of* the problems of theoretical organic cheEnistry which is receiving a great deal of attention at the present time is the investi­ gation of cyclooctatetraene and its related compounds,

Most of the

theories which hsWe been proposed to explain the difference between the type of unsaturation found in benzene compounds and that present in the aliphatic unsaturated compounds call attention primarily to the fact that in benzene there exists a cyclic system of alternate double and single bonds.

To investigate the validity of such theories, Willstat­

ter and Waser Cl)* in 1911* undertook the investigation of cycloocta— tetraene, the next higher ring system in which such an arrangement is possible. Starting with the alkaloid pseudo-pelletierine, these investigators presented the following reactions*

H8304

/

~

7

\

N-CH3

-H ~HCH0 ' OH

degradation

dt§s$?* N(CHg )a Br

Hofmann degradation

\ (l).

Willstatter and Waser, Bar.,,44, 54^5 (1911)*

)

2

Willstatter*a work was carefully performed, and for many years his structural proofs seemed satisfactory. Thus, his cyclooctatriene To « underwent smooth hydrogenation^cyclooctane melting at 11.6 - 11.8 (melt­ ing point of pure cyclooctane s 11.4*), the dibromide when boiled in quinoline solution gave a hydrocarbon 08H8 which hydrogenated to OqHi 4, the latter being described as bicyclooctane, and the cyclooctatetraene was said to hydrogenate to an ‘’impure cyclooctane” of vrhich no physical constants were reported. Thus this work was accepted without doubt up until 1959 when a striking similarity between the alleged cyclooctatetraene and styrene was pointed ouT(2).

A comparison of these two compounds is given in

the table below: Table I Qvclooctatetraene (5) B.P. 42.5 at 17 nun. 0.909

Stvrene B.P. 45*at 17.mm. dI? "9°0.9075

n*0’1.559 1.545 adds Br2 — » 03H8Brs; M.F. 70.-71.5° C6H5CHsBrCHs3r; M.P. 72.-75* ^ § l § vSfbf i B 2 ^ 8 eM eL15i$-5- Br °6H4CH^rCH3Br} M.P. (Sf adds H B r O ^ B r * B.P. 85-7° 06H50HBrCIi3; B.P. 97* at 17 mm. at 12.5 mm. treatment with HM)3 causes resinification

easily polymerizes

Reduction in the presence of Pt black:

Reduction of benzene in presence of Pt black:

1st mole

-- - 55 min.

1st mole - - - 24 min.

2nd mole

-- - 40 min.

2nd mole - - - 59 min. .

5rd mole 4th mole

-- - 40 min. -- - 95 min.

5**d mole - - - 57 min.

The reduction product remained a li­ quid with the most highly purified sample melting at 6.S>*• Oxidation with HH03 gave suberic acid which melted low but which, after several recrystallizations, melted at the correct temperature• (2).

C-oldwasser and Taylor, J. Am. Chem. Soo., 61, 1260 $1959)

(5).

Willstatter and Heidelberger, Ber.,46, 517 U915)

5

The pointing out of this remarkable similarity has stimulated a large amount of research on various phases of this subject since 1959* The reason for the interest in this compound is obvious.

If cycloocta-

tetraene has been made by Willstatter, then it has a type of unsaturation more akin to aliphatic defines than to benzene, a fact which is at vari­ ance with the structural similarity of this compound to benzene*

If cy­

clooctatetraene has not been made, this omission should be rectified to provide a reference ompound with which to test present theories of con­ jugate unsaturation and of the inertness of the aromatic nucleus* Research on the cyclooctatetraene problem has taken three dif­ ferent line3 of approach: 1,

A thorough check of Willstatter's synthesis from various points of views.

2.

Other methods of synthesis,

5*

Synthesis of substituted cyclooctatetraenes* The most direct check up on Wilst'atter'a work is being carried

out at the present time by Linstead at Harvard University.

A reaction

devised by Schopf and Lehrmann (4) has made a source of pseudo-pelletierine readily available.

This synthesis is from glutaric aldehyde and ace-

tonedioarboxylic acid as follows:

OHg(GHsCHO)

COjpHgCOOH)

+

CH3NHS

Linstead is repeating Willstatter*s synthesis with pseudo-pelletierine obtained in this way.

Up to the present time he has met with little suc­

cess in his efforts, and no publications on this work have appeared. A second method of checking up on Willstatter's synthesis is that of Hurd and Drake (5) who have sought to throw some light on Will shat­ ter fs assumption that in each of the Hofmann degradations shown above he obtained a compound containing conjugated double bonds.

A more detailed

discussion of this approach Ofthe problem will be given later. (4).

Schopf and Lehrmann, Ann., 518, 1 U935)

(5).

Hurd and Drake, J. Am. Chem. Soo., 6l, 1945 {1939)

4

Finally, another very indirect check up on Willstatter*s work comes from the field of heterocyclics.

This is an argument which throws

doubt oh Willstatter*s claim that cyclooctatetraene is aliphatic*

It is

an argument of a strictly speculative type, and has little experimental evidence to back it up, but it is nevertheless rather interesting, and seems worthy of mention. prr

prr

It is well known that thiophene,

, is quite similar

to benzene in many of its chemical and physical properties*

This com­

pound, therefore, is often termed aromatic, and it is noted that the sulfur atom is equivalent to a -0H= OH- group.

1,4-Dithiene, S^^ZL^^S,

has also been made (6), and is said to be aromatic in that it undergoes a Friedel and Grafts* reaction. is equivalent to a — CH=rOH—

It is argued that here again each sulfur atom group and, therefore, that the compound which

would be obtained by replacing each sulphur by this group, cyclooctatetra­ ene, would also be aromatic. Independent methods of synthesizing cyclooctatetraene

or other

hydrocarbons containing this ring have been entirely unsuccessful.

Sever­

al of these attempts will be enumerated. Goldwasser and Taylor (2) dehydrogenated cyclooctene over chromic oxide at 400

and obtained a 95

yield of styrene.

This evidence more

than any other lends credence to the suggestion that Willstatter may have obtained styrene as his final product instead of the cyclooctatetraene he reported, although Willstatter*s conditions were not nearly this drastic. Vincent (7) attempted to synthesize 1,5-cyclooctanedione by treat­ ing 1,4-cyclohexanedione with diazomethane, and hoped to be able to put conjugated double bonds into this compound after the 8-membered ring had been obtained.

However, he obtained a mixture of^four products of which 0HS

he identified two heterocyclic substancesi fee OHs °\?

fefeH and

OH*

fee

C=Q CHg

OHa

^OHs

fee:

(6). Levi, Ohem. News, 62. 216 (1890) (7). Vincent, Thompson, and Smith, J. Crg. Chem.

605, (1959)

5

Kohler (8), also in 1959# applied the diazomethane reaction to cyclohexanone and cycloheptanone and obtained cyclooctanone in very siz­ able amounts — about 50 Idlograms being mad© before the synthesis was continued farther* Attempts to Introduce unsaturation into this ring met with the difficulties shown belows

Br Br

+

(very small amount) In a slightly different approach, Steadman (9), at the suggestion of Kohler, treated oC-chlorocycloheptanone with diazomethane to get a 1yjo yield of c^-chlorocyclooctanone.

Treatment with alcoholic sodium hydroxide

caused a Favorskii degradation to cycloheptanecarboxylic acid:

>UH

=0 000H

The third method of attack on the problem is the synthesis of substituted cyclooctatetraenes.

This approacbhas met with more success

thus far than have either of the other two methods, but whether it consti­ tutes a solution to the problem is questionable*

Its proponents theorize

(8). Kohler, Tishler, Potter, and Thompson, J. Am. Ohem. Soc., 6]L, 1057 (9)* .Steadman, J. Am. Chem. Soc., 62, 1607 (19^0)

6

that substituted cyclooctatetraenes may be easier to make, more stable, and yet may serve the purpose of determining whether this 8-membered ring Sys­ tem is aromatie or not#

However, it is quite possible that the properties

of the cyclooctatetraene ring in a compound such as dibenzocyclooctatetraene may be quite different from those of the parent hydrocarbon just as the middle ring in anthracene may enter into reactions of the Diels-Alder type, etc# which are not typical of the benzene ring*. The only one of these substituted cyclooctatetraenes which has actually been obtained was that synthesized by iflfawzonek (10)# This synthe­ sis involves the following steps: 06Hb-C-C00H HsS O ^ C6HB-g-COOH

150 01 o

>Ac

The only reaction of this rather highly substituted cycloocta­ tetraene which was reported was that with bromine.

This was somewhat

peculiar and can best be demonstrated by comparing this reaction with the similar reaotion of the monoacetate*. Both substitute one bromine atom to give the following: (10).

tsfawzonek, J. Am. Ohem. Soc., 62, 745 (1940)

7 Br

OAc

Br

0

OAc

OAc

The monobromo diaoetate is resistant to further bromination, while the monobromo monoacetate adds bromine to give a product which was hydro­ lyzed to a triketone:

0 !

Wawzonek also attempted to prepare eym-dibenzocyclooctatetrene by reduction of the diketone given above followed by dehydration, but this failed beoause of the ease with which this compound bridges to a i* bicyclooctane derivative: OH

Fry and FieBer Ul)i by means of a Thorpe ring closure, have made a saturated cyolooctanone which hey hope will lead td> benzocyclooctatetraene• The last steps of their synthesis are: ON ■OHg-OHg-CN

)

8

Recently Rapson and Shuttleworth :(12), in England, have reported the failure of an attempted synthesis of l,2-3,4-dibenzo-l,3,5,7-cyclodctatetraene $

After a rather involved synthesis, these workers obtained the compound 1,4-bi a-Qo-i odophenyl)-1,5-butadie ne, OH= OH— CH= OH ‘I

Thia compound would not cyclize under the influence of copper bronze alone or of copper bronze inJloiling quinoline, butjwnder such con­ ditions iodine vras detached and 1,4-diphenyl-1,5-butadiene was isolated in 11% yield. Anqlmost identical plan of making this same substituted cyclo­ octatetraene was simultaneously tried by workers at Purdue University (15). These men triedtt cyclize the compound CH=CH— OHrrOH

but were unable to do so.

They explained the failure of the attempt by the

absence in their product of any of the stereochemical f’om(cis, cis-) which would be moat apt to cyclize in the desired way. U2).

Rapson add Shuttleworth, J. Ghem. Soc., 1941. 487-90 Bachman and Hoaglin, page 4 of the Abstracts of Papers delivered before the Organic Section of the American Chemical Society at Memphis, April, 1942.

9

Returning now to the criticism of Hurd and Drake (5) mentioned above, these investigators pointed out that Willst&tter had no grounds for his assumption that the double bonds introduced into his eight membered ring by means of Hofmann degradations were arranged exclusively in con­ jugated positions to each other.

This objection seemed justified, for al­

though a great deal of work has been published on the Hofmann degradation, very little has been done with compounds in which more than one double bond was introduced. When one looks over the work which has been done, it becomes evident that this reaction is one of more complexity than is usually thought to be the case.

Thus in the so-called "normal” reaction, the py­

rolysis of a quaternary ammonium hydroxide results in the formation of a tertiary amine, water, and an olefin: heat (03HB)4lJ0H

>■

Instead of water formed in rare instances.

(C3H5)3N

+

H30

+

03Hi

and an olefin, an alcohol may be The beBt-known example of this is the pyroly­

sis of tetramethylammonium hydroxide where olefin formation is impossible. There are also examples of alcohol formation even when olefin formation seems possible#. Thus in the compounds R(CH3)aN0H where R is hexyl, he|frtyl, octyl, or cetyl, the yield of methanol obtained on pyrolysis is on the order of 75^ (1^)»

Moreover, the other products of the reaction here

are chiefly hexyl, heptyl, octyl, and cetyl alcohols respectively rather than the corresponding olefins* Other examples of anomalous Hofmann degradations are: (1)

The pyrolysis of tetraallylammonium hydroxide (15) yields diallylamine instead of the tertiary amine.

(2) (14).

Some substituted cholines give good yields of an ethylene

C.D. Hurd, "Pyrolysis of Carbon Compounds”, The Chemical Catalog Company, New York, 1929>.page 299

(15).

~

Solonina, J. Russ. Phys. Chem. Soc*, 58. 1286 (1907) via Chem. Abstracts,

2086, (1907)

10

Oxide derir.tlv, (16)s CH3

O sH„

CH

CHOH

°*3 ----- »

(OH3 )3HOH

°6»B

CH-— OH

(OH3 )3N

+

-*■

Ha0

c(

x

Rearrangements or migrations may occurs (a)*

In one oase the wandering of a methoxyl group has been reported (.17)* 9* HONiGU3 )sOHeW O H s —

(b)»

*

(0Ha )3N ~t

Hs0

+

0H30CH= OOHa

A double bond migration occurs in the well-known exhaustive methylation of piperidinet X 0H*

^OHo 0Ha CHS I 0H3

OH

1 ------- ) >1 -GHa OHa

Oh"3h ^OH3 (o).

X 0H 0HS

OHgl

OH

S0H

- T -'o --- * *1 0HS I, etc. w(aHa)8 • OHg

I 0H3

Solonina {15) reports the formation of acetaldehyde from N,1STs-hexaethylethanediammoniua hydroxide.

This may be

explained by vinyl alcohol formation, followed by a re­ arrangement of this product to acetaldehyde: (CsH5 )3M OH

>

fiCH8N(C2H5)3

____ >

COgHeJsNOH^Hg

OH

(Oq Es )qn

OH

+ ["oh^choh)

»

0H30HQ

Since the vinyl, group has a very strong electron affinity, the bracketed quaternary ammonium compound above would be expectedTb break down as indicated.

This supposition is

supported by the fact that neurine, HON{CHq >3CJH^CHa, changes largely into trimethyl amine and acetaldehyde on pyrolysis (l4). U 6;. Rabe and Hallensleben, Ber*, 4^., 2622 11940) Tiffeneau, Oompt..rend., 158, 1580 U9l4)

U7).

u

(d).

The exhaustive mathylation of morpholine gives some rather peculiar results (18).

Here the final products

are acetylene, acetaldehyde, and trimethylamine in spite of the fact that the expected vinyl ether is a known compound (19), and fairly stables (X OHg 1

CHa 1

0H3X " i;'o >

tit

OiT X 9HS 11 I

CHS=CH-GH-GH£ — )> ± 1 1 % 01

CR^OH-CSCH

OH

(32).

Willstatter and Wirth, B§£., 46, 535-6

(1913)

(33)*

Shilov and coworkers, Sinteticheskii Kauchuk 1933, no. 1, 4-12; Ohem. Abstracts, 2£, 5052 (1933)

21

In either case, it is conceivable that some of the 1, 2, 5~ triene may be formed along with the vinyl acetylene*

Such a system of

double bonds has recently been reported ($4) in a highly substituted butatriene, namely, CsHs-GrC=C^Q-06H5 • Another compound related to (VHq

OyHe

butatriene was obtained by Ooffman and Carothers (55), GH3=CHCC1=C=C.sCH2 • This compound Was quite stable, could be oxidized or reduced, and showed no tendency to rearrange* When these Hofmann degradation;experiments we» undertaken, several interesting results were obtained*

First it w&s found that when

the diehlorobutene was treated with trimethylamine in dioxans solution, only the mono-salt. Ql-NCCHa )o-CHo-QH=GH-QIL*Ql. was obtained, since this compound precipitated from the solution before further reaction with the trimethylamine could take place# On the other hand, when methyl alcohol was used as a solvent, or when no solvent at all was used, only the ^i. salt was obtained*

With

solvent absent, however, the yields were somewhat lower and the product was much harder to purify than when solvent was present. The bis quaternary ammonium salt was changed into the correspond­ ing hydroxide, and this was pyrolyzed. obtained*

Gaseous and liquid products were

Analysis showed that vinylacetylene was the only unsaturated

compound in the gas.

The liquid product was a high boiling mixture, and

probably consisted of oxidation products and polymers.

That some oxidation

took place wa> indicated by the fact that the amount of oxygen in the gaseous products was always appreciably less than one fourth of the nitro­ gen present. In as muoh as the mono quaternary salt mentioned above was avail­ able, the possibility of a Hofmann degradation of this compound was con­ sidered*

This reaction was of interest because the expected product of a

normal degradation would be an allene, 4-chloro-1,2-butadienet H0-N(GH3 )^0H8-GH=0H-CHs01

-iassl* 0H2-C-0H-0Hs01 +

(OH3)3K +

Hs0

(54:)#. Simamura, Bull* Chem. Soc. Japan, 16, 210-15 (l94l); via Chem# Abstracts, 56* 760 (1942) (55).

Ooffman and Carothers, J. Am* Chem. Soc., 55, 2040-7 (1955)

22

This alien© i© known (56) to be stable in the absence of cata­ lysts, but undergoes

shift to chloroprene in the presence of auch

catalysts as hydrochloric acid containing cuprous chloride, hot dilute hydrochloric acid alone, hot quinoline (l40-150°), powdered potassium hydroxide, or heat (290°) in the presence of silica gel*

If 4-chloro-

1,2-butadiene were isolated as a product of this Hofmann degradation, it would be the first clean cut, direct evidence of allene formation in such a reaction* This degradation was performed, but instead of obtaining either 4-chloro-l,2-butadiene or chloroprene it was found that the product collect­ ed below 100° contained no halogen (b.p* of chloroprene, 59°; b.p. of 4-ohloro-l,2-butadiene, 88°}*

Methyl vinyl ketone was isolated in small

yield from the reaction products*

The presence of this product, while

not expected, can be explained by the following series of reactionss 01-N(CH3 )3CH2-CH"CH-CHgCl >

-

L OH8 -

u AgsO — ^

I— _ |J3Hg=C=( C=CH-CHsOH |

J^OHgSGH-OHg-CHoJ ----£

0H3-CH=CH-CH0

Another phase of this problem which was developed was the h

possible synthesis of cyclooctatetraeno by cyclization of an open chain 8-carbon1compound.

The original idea was to start with crotonaldehyde and

perform the following stepss 1),

2 QHq—GKSGEt’rGHO ---- >

2).

OH3-OH=CH-CH-CHg-CH=OH-3HO

GH3-GH=OH-GH-GH8-GH=OH-OHO OH OH3-OHsQH-CH-OH-CH=CH-CHO +

Hs0.

oh:

5),

GH3-CH=OH-CH:rOH-GH=OH-CHO

V _ /

4).-

A search of the literature revealed that little is known of such crotonaldehyde condensations*

The aldol type of productshown in step

one is very difficult to isolate, and the reaction has a tendency to pro­ ceed directly to the octatrienal shown in equation two.

Only one person

claims to have isolated the intermediate aldol and this was in very small amounts (57)*

Ihe structure of this product is uncertain*

That the condensation does give a straight chain product is certain for Kuhn (5&) has shown that this condensation follows the prin­ ciple of vinylogy to form octatrienal* (57)*

Ida Smedley, J. Chem. Soo., 99. 1651 (1911)

(58).

Kuhn and Iloffer, Ber.,

2164 (1950) ; Also Ber*, 6k. 1977 (1951)*

24

Step number three would undoubtedly be difficult*

If the

principle of vinylogy holds In an eight-membwred ohain, this would be a reason to expect this ring to close at the position indicated.

To en­

courage ring formation rather then continued linear condensation, it was reasoned that this step should be carried out at very high dilution.

The

principle underlying this conception is that in very dilute solutions the two reactive ends of a molecule will be closer to each other than to the reactive positions of neighboring molecules. densation will be favored.

Hence, intramolecular con­

Here again, if ring closure occurred, the al­

dol probably would not be isolated, but the reaction would be expected to proceed to the final cyolooctatetraene* Toe compound, octatrienal, required for the ring closure above was not readily available from any known procedure.

It has not been isola­

ted from a condensation of orotonaldehyde with itself in the manner indica­ ted in equations U ) and (2) above. An attempt to obtain this aldehyde by a condensation of crotonaldehyde and acetaldehyde as described by Kuhn and Hoffer 15#) yielded only a small amount of sorbic aldehyde, CH3CH=CH0H=®0H0. tte conversion of crotonaldehyde into octatrienal using the high dilution technique was considered, but this line of thought suggested a further simplification of the originally proposed synthesis.

If croton­

aldehyde could be condensed to octatrienal by using high dilution technique, then there seemedTfc be no reason why the cyclization shodid not occur at

the same time. taietraene•

This method would afford a one step synthesis of cyolooo-

Such high dilution work, however, jLs very empirical*

It in-

volves the discovery of the proper catalyst, the most suitable solvent, the best dilution of aldehyde and of the oatalyst, thefrate of feed of toe aldehyde into the reaction kettle, the best methods of preventing side re­ actions, methods of isolating the products, and others. The high dilution apparatus described in detail by Adame and Kornbloom (59) was built with only one slight modification, toe attachment of a stopcook to toe orotonaldehyde reservoir to facilitate emptying the, (59).

Adams and Kornbloom, J. Am. Ohem. Soc., 62, 188 (ip4l)

25

mercury from this chamber at the end of the reaction*

A number of experi­

ments have been performed with thie apparatus, but only a start has been made in determining whether or not this is a feasible method of synthe­ sizing cyclooctatetraene. A few interesting discoveries have been made.

Up to the present

moment, only methyl alcohol has been used as a solvent.

Sodium .methoxide,

zinc chloride, and potassium carbonate have been used as catalysts.

Vary­

ing amounts of sodium methoxide and several dilutions of crotonaldehyde were studied. One pronounced limitation of the process is the fact that much of the crotonaldehyde seems to undergo linear polymerizations

Moreover only

small amounts of crotonaldehyde can be used, for an excess of this reagent would react with any octatrienal or other aldehydes formed as primary pro­ ducts and deflect the desired course of reaction.

From 14 g. of croton­

aldehyde, generally only about two to three milliliters of distillable pro­ duct is obtained.

No crotonaldehyde is usually recovered, and all of th*

rest is converted into tars. The condensation with potassium carbonate was slow, but complete. No distillable product was obtained. When zinc chloride was tried as a condensing agent, only a small amount of the orotonaldehyde was condensed, and this to tars. The most interesting results were obtained using sodium methoxide as catalyst. used.

The results depended a great deal upon the amount of sodium

When three moles of sodium to one mole of crotonaldehyde was used, the

reaction was very rapid, and went to undistillable polymers.

When only 0.5

mole of sodium per mole of crotonaldehyde was used, the reaction was incom­ plete, and the products were polymerized less extensively.

Some oroton­

aldehyde was unchanged and. this was isolated as the dimethyl acetal after acidification of the reaction mixture with formic acid.

About 5 ml. of dis­

tillable polymers were obtained. Among the few products of the self-condensationnof crotonaldehyde which have been identified and described are 1,2-dihydro-o-tolualdehyde, b.p. 71-75° (12 mm.), and an unidentified unstable aldehyde , hp. 97*98° (12 mm.), obtained from this aazas reaction (4o). (4o).

The first of these pro-

Berhhauer and coworkers, Biochem. Z. , 249. 199 (1952); 25k

175 (1952);

254. 45A-7 (1952); Chem. Abstracts, 26, 4581, 5907 (1952); 22., 268 (1955)'

26

ducts is presumably obtained through a condensation involving a hydrogen on the 4-oarbonnof one of the crotonaldehyde molecules:

nun OHO oh, Nao

+

9H0 (Jh

L

—

Cfl3-CH §„ OH

»

0H3

H OHO

1 OH

—

*

J* ° m ,

OH

1 N;

Thaso products were looked for among the distillates from the high dilu­ tion run.using half molar quantities of sodium, but none of our products boiled as low as these compounds*. Finally, a high dilution experiment was rim using one mole of sodium for every mole of crotonaldehyde* half a gram of solid was obtained. octatrienal*

From this run a little over

This solid was first thought to be

Such a slight precipitate was formed with 2,4-dinitrophenyl-

hydrazine, however, that it could have been due to an impurity or to an unexpected side reaction.

Moreover, its melting point was

that reported by Kuhn (58) for octatrienal.

15°

higher than

This compound was finally

shown to be identical to the monohydrate of 2,6-dimethy 1-5,6-dihydro-Hpyrane-5*H3arboxylio acid described by Delepine (4l):

OHe-CHSCH-GOOH I I GHg -CH— G--. Found *;Br,, 58*47^* The yield in this experiment was low because of loss of much salt while trying to find a suitable recrystallizing solvent* Subsequent experiments, however, gave yields of 75-85^«. Reactionnof 4-Bromo-2-pentene with other amines* a)*

With ipyridine t: Twenty grams of 4-bromo-2-pentene and 12 g* of dry pyridine were mixed without the use of a solvent*

The reaction was

complete after setting at room temperature overnight.

The solid was

collected on a filter, and after three recrystallizations from alcohol melted at 215°.

This is the melting point given in Heilbron^

Dictionary of Organic Compounds for pyridine hydrobromide* metric analysis of this compound gave the following results:

A gravi­

22

jaalygiss subs., 0*4466 g.; AgBr, 0.5204 g., Calc’d. for C5H6NBrt Br,,50.0$ Founds Br, 49.5$ ' b).

m t h morphoUnes Ten grama of 4-bromo-2-P0ntene was added to 6 g. of morpholine, a compound which is known to be an effective dehydrohalogenating agent.

This reaction was instantaneous.

The solid formed

was filtered off and recrystallized twice from alcohol; m.p. 205®.. This is the melting point of morpholine hydrobromida.

The analysis

of this compound also showed it to be this hydrobromide: Aflalyais: subs*, 0.4400 g.; AgBr,,0.4922 g.. Oalc *d. for 04H100NBri;Br, 47.8$ Found: Br, 47.5$ 0)0 &S?. jimethylaniline:

Twenty grams of 4-bromo-2-pentens was put in

a tightly stoppered flask with 17 g. of dime thylaniline. tion was very slow and incomplete.

The reac­

The flask was put in the ice box

to induce crystal formation, since a previous experiment had indica­ ted that oils are formed in this reaction.

A few small crystals had

formed by the end of the first day, but these turned into an oil dur­ ing the second day, and crystals could never again be obtained from this oil. No trace of pentadiene could be found in the flask. M ftgbjons.,.in -WhiCh:il.5-Pentadiene was Formed as a Bv-prndnc+.. a>* Iteft 3 Grignard reaction:

This reaction was carried out as described

on page 28 with the only variation being in the proportions of tha reagente.

Five hundred grams (5.56 moles) of methyl iodide and 100 g.

(4.11 moles) of magnesium were used to form the Grignard reagent. The color of this Grignard reagent solution was much darker than usual.

Two hundred twenty-five grams of redistilled, middle-cut

16Jt.f

crotonaldehyde (5*2 moles) was added until the dark color of the Grig­ nard reagent had taken on a greenish tinge.

After standing overnight,

the product was hydrolyzed in iced dilute sulfuric acid.

It was ex­

tracted with ether, dried over calcium chloride and distilled.

A cut

was taken after the material boiling below 120° had been taken off. However, it was noticed that the temperature fluctuated between 100 and 123° while the material seemed to be coming through the condenser

55

at a constant taking place.

It seemed as though some decomposition were A little water also came over in spite of the fact

that the liquid had been well dried before the distillation. The distillate was dried over a few sodium hydroxide pellets and redistilled.

The distillate had been slightly colored,

and as this was thought to be due to air oxidation a little hydroquinone was placed in the receiver.

A water bath «as used to heat

the flask in this second distillation, and the product came over slowly.

Twenty-six grams of l*2-pentadiene boiling at 42° was ob«*

tained before the boiling point began to rise. the material was vacuum distilled.

The remainder of

The forerun consisted of about

10 ml. of highly colored liquid, then 56.8 g. of 5-pentene-2-ol~ came over.

About 20-25 ml. of residue remained in the flask.

The

5-pentene-2-ol boiled at 71-74° at $6 mm., but although it seemed fairly pure , a very low yield of 4-bromo-2-pentene (21?*) was obtain­ ed on subsequent treatment of this alcohol.with hydrobromic acid according to the directions given on page (29)b).

From the splitting of dipentenyl ether; In his original article (26)*, Boudringhien mentioned that dipentenyl ether can be split by concen­ trated hydrobromic acid, but he gave no details of this splitting, either as to the laboratory procedure used, or the products and yields obtained. Fifty-eight grams of dipentenyl ether Oikp. 158°) was put in a 200-ml., round-bottomed flask.

This was placed in an oil bath at

150-153° and redistilled constant-boiling hydrobromic acid was added drop by drop. two layers.

The liquid whioh distilled from the flask settled into The bottom layer of hydrobromic acid was about a fourth

as large as the top layer.

The top layer was separated, washed with

water and sodium bicarbonate; yield, 55 g.. After two distillations, this top layer was separated into three definite fractions.

These consisted of 12*7 g* of 1,5-ponta-

diene boiling at 41-42°, 15 g. of a fraction boiling between 115 and 125° which was chiefly 4-bromo-2-pentene and perhaps a little 5“P®B“ tene-2-ol, and 5 g. of unchanged dipentenyl Ather which had steam distilled.. There was a little high boiling residue, but most of the remainder of the 58 g* of ether originally taken remained as a top layer in the reaction flask.

OO

P

I of one of the substances* b)*

Bv analysis with an Or aat apparatus: itfhen the Or sat apparatus was used, some very good figures were obtained. Tabid VII*

These are shown in

The results were reproducible and v/ere believed to be

accurate to within a few tenths of a percent*

layer was

4i

Preparation of the Mono Salt of 1.4-Pichloro-2-butene. The dichlorobutene was distilled through a Vigreux column and a cut whose boiling point range was 157-159° was taken for use.

Fifty-

grams of this material was dissolved in 200 g* of dry dioxane, and 51 g. of liquid trimethylamine was added to this solution* cipitate almost instantly.

Solid began to pre­

This mixture was allowed to set for two days,

the white solid was filtered off, sucked dry, and was placed in a vacuum desiccator over concentrated sulfuric acid which removed the adsorbed trimethylamine from the salt.

Sixty-seven grams of crude product was ob­

tained, which represents a 69$ yield.

However, this salt was still slight­

ly colored, and it melted over a 12*1*ange*

It was further purified by

four re crystallizations from absolute alcohol.

The first and second crop

of crystals together weighsd 51 g* * The product was pure white, and melt­ ed at 174-176°.

This product could not be analyzed in water solution for

the chloride ion, for much of the carbon-bound chlorine is hydrolyzed in the process.

This is to be expeoted since this is an allyl chloride type

of halogen, and hence is very labile.

The product was analyzed for total

halogen by the method of Vaughn and Nieuwland (47) using 3odium in liquid ammonia to dehalogenate the organic compound. Analysis;

Subs., 0*4791 g.* AgOl, 0.7204 g. Oalc’d for 07HXSNC1S : 01, 5Q.6 $ Found: 01, 57*2. $

Preparation of the Pi Salt of 1.4-Pichloro-2-butene. a).

Using a methanol solvent: Thirty-five grams (0.28 mole) of redis­ tilled l,4-dichloro-2-butene was dissolved in 200 g. of methanol.

This

bottle was connected to the system in which the trimethylamine was generated and liquified, and was weighed at intervals to determine the amount of trimethylamine added.

Ihe reaction was stopped after 40 g.

^0.68 mole) had been added during which time the methanol solution turned a dark red color. No precipitation occurred in the flask on standing.

After

three days, the bottle was opened, and its liquid contents were distil­ led into dilute hydrochloric acid to absorb any unused trimethylamine. The solid was filtered off, sucked dry, and left overnight in a vacuum desiccator over concentrated sulfuric acid.. 47).

Vaughn and Nieuwland, Ind. Eng. Chem., Anal. Ed., I, 274 (.1951)

42

Recrystallization was difficult, and norite was ineffec­ tive in removing the color*

After four recrystallizations from

absolute alcohol, the product melted at 261® with decomposition* Ihs crystals were white and were rather granular*

The yield was

20 grams of pure product, or 29.4/0 of the theoretical amount.

An

analysis for ionic chlorine from a water solution was about 2y« low* An analysis by the method of Vaughn and Nieuwland (47) gave the following figures*. Analysis:

Subs., 0*5477g*j AgCl, 0.4060 Calc4d for Ci0He4NsCla:. Cl, 29.2/i Found: Cl, 23*9%

It is possible that the percentage of chlorine found by this method; was slightly low because the di salt is rather insoluble in the liquid ammonia solvent*, b)*

Using no solvent: Thirty-five grams of l,4-diohloro-2-butene was put in a bottle connected with the trimethylamine generator as in the preceding experiment. ed*

Forty grams of liquid trimethylamine was add­

Considerable trouble was encountered with the mixture solidify­

ing to a hard mass which the trimethylamine could not penetrate, and this had to be broken up from time to time. This mixture also darken­ ed considerably as the trimethylamine was added* This bottle was opened after standing for three days, and its liquid content distilled into dilute hydrochloric acid*. Recrystallization of this compound Was extremely difficult, and a product of purity comparable to that obtained in the methanolL run waq&ot obtained after five recrystallizations.

Several times

during this recrystallization,very viscous, dark, hopeless-looking residues were obtained, but after concentration and standing in the cold room for several days, some solid was obtained from these mix­ tures.

Ihe beat sample obtained from this run melted at 254-255°.

The yield was 18 g. of a rather crude product. Hofmann Degradation of the Mono Salt. Thirty-one grams of the mono salt was shaken for forty-five minutes with silver oxide.

The mixture became very warm, and the odor

45

trimethylamine was apparent* A 60/fc excess (31*5 g*) of silver oxide was used as usual to offset the fact that some of this oompound becomes coated over with silver chloride during the reaction and it is not all available for hydroxide formation*

The solution was filtered and the

silver chloride and oxide washed with water* The water solution of the quaternary ammonium hydroxide was placed in a dropping funnel §nd dropped into a Olaiaen flaak heated to 160° in an oil bath.

After most of the water had been removed, the tem­

perature of the oil bath was raised.

The degradation seemed to proceed

very slowly below 230°* Analysis of the Pvrolvsia Products* The mixture of degradation products was extracted with ether.

The

odor of crotonaldehyde polymers was quite apparent from time to time dur­ ing the extraction* duct remained*

After the solvent had been removed, only 3 eiI* of pro­

This, on distillation, began to boil when the oil bath temp­

erature reached 100$#

About 0*5 ml* was obtained boiling constantly at 77°•

The higher boiling product was distilled under a vacuum, but was a mixture of oxidation and polymerization products from which no pure compound could be isolated*

This material darkened on standing and smelled exactly like

crotonaldehyde polymers*

It gave a very slight precipitate with 2,4-dinitro-

phenylhydrazine• A micro boiling point was taken on the low boiling fraction by the Sowoliboff method and also was exactly 77° ♦ The refractive index ac. 20° was found to be 1*3801*

The Z reading was4l.

The density was measured as

0*86, but could not be obtained any more accurately than this because of the small amount of liquid available*

A precipitate was formed with

seraicarbazide which melted at 125-131° $ but the tiny amount of this material available prevented it from being recrystallized*. Except for the refractive index, these constants check well with those given for methyl vinyl ketone (48) by Krapuvin,,namely b.p*,78-80°* dj°0*8636, nj^° 1*4086 (48)*

semicarbazone m#p* l4o-l4l°.

Krapuvin, Bulletin de la Societe Imperial des Naturalistes de Moscou, 1908. 1-76* Ohem. Zentr*, 1910. I, 1336

44a

Table VII Analysis of the Product of Pyrolysis Run 1 Run 2 Sample, ml* 99*1 99.4 Burette Reading after

78*2 Maleio Anhydride Abaorp - 77-5 tion, ml* 16.6

Run 5 99.9

78.5

16.2

7 70 77.25

15.9 12.1

16.5

77.2

71.8

16.25

77.2

71.8

Burette Reading after

75*2 75.0

75.9 75*9

70.2

Sulfuric Acid Absorp­ tion, ml*

70*2

75*0

2,2-Pentadiene, %

5.2

5.5

5.4

Table VII£ Analysis of the Product of Pyrolysis Run; 1

Run 2

92.0

92.1

Burette Reading after

90.25

89.0

Potass iuDi Mercuriiodide

90.5

89.0

Absorption

90.5

Burette Reading after

90.5

89.0

Sulfurio Acid Absorption

99*5

89.0

Burette Reading after

15*5

73.2

Alkaline Pyrogallate

15*5

73.2

Sample, ml*

Absorption

44

Hofmann Degradation of the Pi Salt,

Twenty grams of the di salt

was shaken for

forty-fiveminutes

with 29 g* of silver oxide and allowed to set overnight before filtering* The odor of trimethylamine was noticed when the shaking was begun*

Also,

the mixture warmed spontaneously* The filtered solution was dropped as before into a 125-ml* Olaisen flask heated to 160° in an oil bath*

After all of the water had

been driven off, the temperature of the oil bath was raised to 210°, and then the flask was brushed cautiously

with a low direct flame. The gas­

eous products were collected in a large bottle over water*

The system

was filled with water at the end of the pyrolysis to force all of the gases into the bottle* Analysis of Hie Products of Pyrolysis The gas was force from the bottle by adding water from a dropp­ ing funnel.

This was passed slowly through a bubbler containing about

1-2 ml* of hydrochloric acid to absorb any trims thylamine remaining in the gas*It

was then passed over dehydrite to remove the water vapor,

and intothemeasuring burette of the Orsat

apparatus*

It was found that

some gas was absorbed in alkaline potassium mercuriiodide solution (49) with the precipitation of a white solid, and none was then absorbed in 05% sulfuric acid* This shows that the gas contains no unsaturated com­ pounds except vinylacetylene*

The results of two analyses are summarized

in Table VIII* The fact that more absorption took place in the potassium mercuriiodide in the second run than in the first does not mean that the two runs do not check, for

the sample

in the first run contained

someair

which had not been flushed

out of the

system, and hence was more

dilute

in vinyl acetylene than was

the sample

in run number two*

It should be noticed

that the amount of oxygen absorbed by

the pyrogallate solution is less than one fourth of the volume of nitrogen left in the system*

This indicates that some of the oxygen was used up

in an oxidation reaction during the pyrolysis* (49).

Hurd and Spence, J. Am. Ohem* Soc*, 51. 3357 (1929)

45..

Description of the High Dilution Apparatus. This apparatus was built almost exactly according to the des­ cription of Adams and Kornbloom (59)*

A diagram of it appears in figure A*

In high dilution experiments with crotonaldehyde, the methanol solvent and the catalyst were placed in the reaction flask (A)*

This flask was fitted

with a motor-driven stirrer operating through a mercury seal*

This arrange­

ment isn't entirely satisfactory as some solvent usually distills into this seal and washes a little of the mercury into the reaction flask.

A stain­

less steel stirrer with ball bearings and a packing box would eliminate this difficulty. Flask ^A) is heated, and the solvent boils out through arm (B) which is heat insulated with magnesia lagging.

The solvent vapors con­

dense in the bulb condenser (0) and flow down the inclined tube to CIS). The bulb condenser may be fitted with a calcium chloride tube (D).

The

bend (E) fills up with solvent, and this prevents the solvent from dis­ tilling through the system in a counter-clockwise direction.

The solvent

flows from (E) back into the flask. A dilute solution of crotonaldehyde is placed in the chamber (&.)• Mercury from a reservoir is allowed to drop slowly into (Cr).

The rate of

flow of the mercury is regulated by the height of the reservoir and by a pinoh clamp (H).

The drops of mercury slowly push the solution of croton­

aldehyde from (&) into the reaction system.

Here it is caught by the

stream of solvent flowing around the system, and is greatly further diluted by the time it reaches flask (A) containing the catalyst which makes the condensation take place.

(Q.) was provided with a stopcock (I) to permit

drainage of the mercury without dismantling this part of the system.

An

obvious improvement would be a stopcock at the bottom of the bend (.E) to allow the drainage of solvent from this part of the apparatus when one wishes to use a different solvent.

In Adams apparatus this can be removed

only by flushing out with the new solvent or by dismantling the whole apparatus. (F)

is a short condenser which condenses the vapors which distill

into this ana of the system.

These condensing vapors help in further dilut­

ing and mixing the crotonaldehyde solution as it flows through this tube. However, with solvents boiling as high as 100°, this condenser cannot be used or at beat a very slow stream of water may be run through it for the conden­ sation of vapors in this arm prevent the solvent from distilling as high as condenser (0) and flowing around the system at a rapid rate*

46

The right hand arm is connected to the rest of the system by a rubber connection at (j) rather than by a glass-to-glass seal to land flexibility to 1He apparatus and to lessen the possibility of breakage of one long, rigid tube of glass. SUft Dilution Condensation of Orotonaldehyde Osins- 0.5 Mole of Methoxide aa Qatalvat> Two grams (about G#1 mole) of sodium was added in small.pieces to 1200 ml..of methanol in the reaotion flask. Fourteen grama (0.2 mole) of crotonaldehyde was dissolved in 500 ml. of methanol, and this was let into the flask as deeoribed above over a period of forty-five hours (not continuous).

This solution was made slightly aoid,with formic acid, and

then the solvent was distilled off through an efficient, large-bore (5.2 cm.) column packed with glass helices and equipped with a totalreflux partial-take-off head# The residue was taken up-in ether and dried overnight with cal­ cium chloride. After removing theether.thie was vacuum distilled with­ out a column, but only a bent tube. A little over one ml. of material came over below 75® (oil bath temperature) at 6 mm.

A yellow liquid dis­

tilled at about 120® (oil bath temperature) and 2 mm.

Finally two very

viscous cuts of about 0.5 ml. each were obtained by heating the oil bath to 280®, and then by heating with a free flame, all at 2 mm..pressure. These four cute were then more carefully distilled through a small fractionation outfit under 5 mm. pressure. clear, colorless liquid boiling under 100®.

The first fraction was a

The second was a fluid yellow

liquid boiling from 110-151®. The third fraction, a semi-viscous liquid, would not distill through the small column. The fourth was a very dark Viscous liquid# About one ml. of the material in the first cut above was obtained. It had a micro boiling point at atmospheric pressure of about 120®. It seemed insoluble in water, but was found to dissolve on standing.

The water

solution gave a precipitate with 2,4-dinitrophenylhydraaine. The odor re­ sembled that of an acetal, and the compound was finally shown to be dimethyl crotonal, a known acetal boiling at 12b®(50).

(50).

Helferich and Hauser, Ber., SJ_, 795-799 (1924).

*7#

No known compound was identified among the higher boiling pro­ ducts# dilution .Condensation of Crotonaldehyde Using Molar Amounts of Sodium Mathoxide as Catalyst. Four grams of sodium was cut into small pieces and added to 1500 ml# of methanol in the reaction flask# Fourteen grains of croton­ aldehyde was dissolved in 500 ml. of methanol, and this solution was run into the reaction system as described previously# tinuous and required about thirty-eix hours.

The run was nearly con­

The reaction mixture became

colored almost as soon as the reaction was begun, and was very dark red at the end of the run#

A dark colored solid precipitated on the side of the

reaction flask above the liquid level# This solid was soluble in both ace­ tone and concentrated hydrochloric acid# At the end of the run, the solvent was distilled off through the efficient column mentioned in the previous experiment, ffhen most of the solvent was gone, the solution was acidified with a slight excess of acetic acid# Water was added to dissolve any unreacted crotonaldehyde, and the mix­ ture was extracted with ether* The ether extract was dried for ten hours over calcium chloride, the ether, was removed, and the residue was distilled through a 125-ml* mod­ ified Olaisen flask* condenser#

Very soon a pure white solid began to sublime into the

The rest of the material in the flask would not distill, but

seemed to polymerize as the flask was heated until it became almost a solid mass# About 0.5 g. of the solid was obtained* This was recrystallized from benzene and melted at 68.5-71.5° depending upon the rate of heating. The solid had a rather sweet odor when first obtained, but on standing, even after recrystallization from benzene, it developed a rancid odor like that of butyric acid*

This apparent deterioration, however, did not effect the

melting point of the compound. ether, acetone, and alcohol.

The compound was soluble in water, benzene,

Its solution in water was acidic to litmus.

Its properties seem to identify it clearly as the heterocyclic acid desorbed by Delepine (4l)*

48

SUMMARY 31* The synthesis of pentenyl trimethylammonium hydroxide has been des­ cribed. 2.

It has been definitely established that 1,3-pentadiene is quantita­ tively absorbed by maleic anhydride at 100°•

5*

It has been shown that the Hofmann degradation of pentenyltrimethyl-

4.

ammonium hydroxide yields a hydrocarbon which is 95% 1,5-pentadiene. A method of obtaining either the mono or the di trimsthylammonium salt of 1,4—dichloro—2—butene has been discovered.

5.

The Hofmann degradation of the mono trimethyl ammonium salt of 1,4-dichloro—2-butene gives methyl vinyl ketone in small yield.

6. The Hofmann degradation of the di trimethyl ammonium salt of 1,4-dichloro-2-butene gives vinylacetylene and no other unsaturated hydrocarbon. 7.

The condensation of crotonaldehyde in the presence of molar amounts of sodium methoxide has been shown to yield the monohydrate of 2,6—di­ methyl -5, 6-dihydropyrane-5-carboxylic acid when carried out in a very dilute methanol solution.

49

BIBLIOGRAPHY 1*

Willstatter and Waser, Ber., 44, 5455 (1911)

2•

Goldwaaser and Taylor, J. Am* Chem. Soc., 61. 1260 (1959)

5*

Willatatter and Heidelberger, Ber., 46, 517 (1915)

4*

Schopf and Lehrmann, Am*, 518. 1 (1955)

5*

Hurd and Drake, J. Am. Ohem. Soc., 61, 1945 (1959)

6. 7* 8.

lievi, Ohem. News, 62, 216 (1890) Vincent, Thompson, and Smith, J. Org. Chem.,

605 (1959)

Kohler, Tishier, .Potter, and Thompson, J. Am* Ohem. Soc., 61,

9*

1057 (1959) Steadman, J. Am. Ohem. Soc., 62, 1607 (1940)

10.

Wawzonek, J. Am. Ohem* Soc., 62, 745 (1940)

11.

Fry and Fieser, J. Am. Ohem. Soc., 62, 5489 (1940)

12.

Rapaon and ehuttleworth, J. Ohem. Soc., 1941. 487-490

15*

Bachman and Hoaglin, page 4 of the Abstracts of Papers delivered before the Organic Section of theAmerican > Chemical Society at Memphis, April, 1942

14.

0. D. Hurd, Pvrolvaia of Oarbon Compounds. The Chemical Catalog Company, New York, 1929# page 299

15.

Salonina, J. Russ. Phys. Ohem. Soc., 58. 1286 (1907)}, Ohem. Abstracts, 1,, 2086 (1907)

16.

Rabe and Hallensleben, Ber., 45, 2622 (1910)

17*

Tiffeneau, Oompt. rend., 158. 1580 (1914)

18.

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51

VITA

Elwood Henderson Ensor Borns

February 1* 1918 at Baltimore, Maryland

Education:

Evanston Township High School, 1930-193** B* S. degree, Northwestern University, 1938 M* A* degree, Boston University, 1939 University of Illinois, 1939-1940 Northwestern University, 19^0-1942

Positions Held: Teaching Fellow in Organio Ohemistry,,Boston University, 1938-1939 Analytical Chemist, Department of Fhjrsiology, University of Illinois, 1939-1940 Men's Chemistry Tutor, Northwestern University, 19^0-19^*1 Assistant in Chemistry, Northwestern University, 1940-1942 Married s

February 14, 1941 to Mary Louise Allen

Daughter Born:

Nancy Joan Ensor, December 6, 194-1