June 20, 1952
2987
THERMAL REACTION OF FORMALDEHYDE WITH ALLYLCYANIDE [CONTRIBUTION FROM THE CHEMISTRY LABORATORY, UNIVERSITY
OF
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The Thermal Reaction of Formaldehyde with Allyl Cyanide BY CHARLESC. PRICE,GEORGEA. CYPHER',~ AND I. V. KRISHNAMURTI~~~ RECEIVED DECEMBER 6. 1951 Thermal condensation of formaldehyde with allyl cyanide a t temperatures above 130' occurs primarily a t the active methylene group. After four hours a t 150",a 28% yield of 2-hydroxymethyl-3-butenonitrileand a 55% yield of the dimer of its dehydration product, 2-cyanobutadiene, were obtained,
A previous report3 has shown that attempts to carry out acid-catalyzed condensation of formaldehyde with the double bond of allyl cyanide failed because of more rapid reaction of the aldehyde with the nitrile group. Since some substances, such as P-pinene4 and methylenecy~lohexane,~ have been shown to react with formaldehyde thermally, this reaction has been investigated for allyl cyanide. If reaction had occurred as for P-pinene, the primary product of the reaction would have been 5-hydroxy-2-pentenonitrile (I). All evidence indicates, however, that primary condensation occurred not a t the double bond, but a t the active methylene group to yield 2-hydroxymethyl-3butenonitrile (11).
TABLEI SEALED-TUBE REACTIONS OF EQUIMOLAR QUANTITIES OF ALLYLCYANIDE AND PARAFORMALDEHYDE Temperature, 170 f 5' Temperature 150*5' Time, hr.
Paraformaldeh de consumed,
1.0 2.0 4.33 8.25 9.25 22.0
23,25 35,41 62,63
6
70 70 87
Time, Paraformaldeh de min. consumed,
&
25 45 90 140 215 320
45 60 68 70 80
88
few per cent. were usually obtained. The results for the two temDeratures studied are given in Table I. AS a result of &ese experiments CHt=CHCHzCN CHeO H°CH~CH~CH=CHCN two large runs were made at 150' 150'44 hr. I in a rocuking, stainless steel bomb. One reaction was stopped after CH,=CH-C-CN CH=CHz four hours, the other was camed tar on for 30 hours. The product CHzOH from these reactions was a heavy, yellow, homogeneous liquid, eff er11 (28%) I11 IV (55%) vescing unreacted formaldehvde. In preliminary experiments, allyl cyanide and Vacuum distillation of ;his liquid gave water,'unparaformaldehyde were heated a t reflux tempera- reacted allyl cyanide containing some paraformture with stirring for many hours a t atmospheric aldehyde, two main fractions (A and B), and some pressure without any reaction occurring. When resinous material. aluminum chloride or stannic chloride was added The higher-boiling fraction B was induced to as catalyst, a low-melting white crystalline solid crystallize by cooling in ice-water. Recrystallized first formed, probably a, complex of the metal from an ethanol-water solution, i t melted sharply halide with the allyl cyanide, and then a violent a t 54.5'. Analysis and molecular weight deterreaction took place. Even when hydrocarbon mination indicated that it was a dimer of cyanodiluents were used and external cooling was applied butadiene. Saponification with aqueous alkali only orange or brown polymers could be isolated produced an acid whose analysis and neutral from the reaction. equivalent were in accord with this. Catalytic The thermal reaction without catalysts was next hydrogenation showed this acid had two carbonstudied in small sealed glass tubes containing 0 001 carbon double bonds. The first mole of hydrogen mole each of allyl cyanide and paraformaldehyde was absorbed very rapidly and the second mole was placed in an oil-bath a t constant temperature and added more slowly. agitated occasionally for varying lengths of time. The melting point of the unsaturated acid (238') The tubes, when removed from the bath, were was nearly the same as that reported' for the acid cooled in Dry Ice and then broken open. The obtained from saponification of the dimer of 2contents were analyzed for formaldehyde using the cyano-l,%butadiene (m.p. 236"). However, since method of D'Alelio.s Working with such small the dimer of 2-cyano-1,3-butadiene has a melting quantities it was not possible to attain the highest point (55-56') very near that of the dimers of 1accuracy in these experiments, but checks within a cyano-1,3-butadiene (53-54") and since no acid has been obtained from the latter, further identifica(1) General Tire and Rubber Company Fellows (I. V. K., 19461948: G. A. C., 1949-1950). tion was undertaken. (2) Abstracted from the Ph.D. dissertations submitted to the GraduThe unsaturated dibasic acid was heated with ate School by I. V. K. and G. A. C. Presented by title a t the XI1 palladium-on-charcoal catalyst containing a little International Congress, New Y o r k , September 10, 1951. copper-chromite catalyst. Carbon dioxide and JOURNAL, 7 2 , 5334 (3) C. C. Price and 1. V. Krishnamurti, THIS (1950). hydrogen were evolved and pure p-ethylbenzoic (4) J. P. Bain, ibid., 68, 638 (1946). acid was isolated from the residue. I n addition, (5) R. T. Arnold and J. F. Dowdall, ibid., 70, 2590 (1948). \
I
+
+
(6) G. F. D'Alelio, "A Laboratory Manual of Plastics and Synthetic Resins," John Wiley and Sons, Inc., New Y o r k , N. Y . , 1943, p. 111.
(7) C. S. Marvel and N. 0. Brace, THIS JOURNAL, 71, 37 (1949). (8) H.R. Snyder and G. 0. Poos, ibid., 71, 1395 (1949).
the infrared spectrum of fraction B gave exactly liquid, distilled a t 102-104° (0.25 mm.). Both the same five characteristic absorption l m i d s he- liquids had an overpowering odor very similar to I ween 4.5 arid 6.7 1.1 as those yeported for 1 \‘.7 that of butyric acid. The lower-boiling acid was shown to be ar-ethyl’The lower-boiling fraction A from the reaction of equal moles of allyl cyanide and paraformalde- acrylic acid (VI)hyits physical constants, neutralizahyde a t 1.50” was foiiiirl to g i w a positive test with tion eqiiivalent and preparation of the amide and both of which were previously ceric nitratc reagent. I t dccolorizcd kmiriirie iu the ~~lieriyll~yrlrazide, carbon tetrachloride, was solublc in water and dis- reported in the literature.IO The higher-boiling acid was shown to be acolored aqueous potassium permanganate. Xnalysis of the material and of its p-nitrobenzoate ethylhydracrylic acid (VII) by its physical conderivative indicated it was an unsaturated hy- stants, neutralization equivalent and the preparadroxynitrile formed by the condensation of one tion of its phenylurethan.” Experiment indicated that no appreciable reacmolecule of formaldehyde with one molectile of tion occurred between crotononitrile and formallyl cyanide. Several attempts to separate the material into aldehyde under conditions where considerable conindividual components with activated alumina and version occurred for allyl cyanide. This rules out other adsorbents such as “Florosil” and alumina of as a possible mechanism the isomerization of allyl various degrees of activity failed to give a separa- cyanide to crotononitrile followed by Prins-type tion. The material was also carefully distilled condensation at the double bond of the latter. It also seems unreasonable to believe that the under reduced pressure. Although this distillation indicated a reasonable reaction proceeds via full ionization of an a-methyldegree of homogeneity (d?j 1.009-1.012, W * ~ D1.4635- ene hydrogen, since the resulting anion would pre1.4688, X R ? 5 26.34-2G.il j the infrared spectra sumably isomerize to establish conjugation of the of several fractions were examined. In the region double bond and the nitrile group.12 Perhaps the of the nitrile absorption, a single strong band was most reasonable picture for this process would inobserved a t 4.48 to 4 3 2 p. This is somewhat volve an electrophilic displacement a t the alonger wave length than for a normal nitrile but methylene group, either by a concerted or pseudoeither conjugation7or a @-hydroxylgroupgpromotes cyclic process (A) or by a process similar to Sh’l disa shift in this direction. In the region of the carbon- placement (B) . The approximate second-order carbon double bond adsorption: a single strong band was observed a t G . O i p, clearly ---cI-r2 ---CHp indicating lack of conjugation between the nitrile and the double bond. The infrared ( A ) CI-II / O H A OH ,CH
