E. E. MAGAT, B. F. FARIS,J. E. REITHAND L. F. SALISBURY
10% [CONTRIBUTION FROM
THE
Vol. 73
CAROTHERS RESEARCH LABORATORY, RAYON TECHNICAL DIVISION,E. I. DU PONT DE NEMOURS & co., 1NC.I
Acid-catalyzed Reactions of Nitriles. I. The Reaction of Nitriles with Formaldehyde1 BY
EUGENE E. MAGAT,BURT F. FARIS,JOHN E
REIrII AND
L. FRANK SALISBURY
Nitriles react with formaldehyde in strong sulfuric acid solutions (65 to 100%) a t room temperature to give yields of methylene-bis-amides often exceeding 90% in less than one hour. The reaction is applicable to other aldehydes, but yields are markedly reduced. Methylene-bis-amides in sulfuric-formic acid solution undergo amide interchange when nitriles are added to the reaction mixture; the new nitrile appears as a component of the new methylene-bis-amide equilibrium mixture.
In the course of studies dealing with the reaction
on the carbon atom adjacent to the carbonyl group undergo a number of self-condensation reactions sulfuric acid solution to form diphenylmethanes, it under the influence of sulfuric acid, and therefore, was found that p-tolunitrile gives none of the ex- give markedly lower yields in the reaction with nipected diphenylmethane derivative but only meth- triles. The reaction is general with nitriles and ylene-bis-p-toluamide. A similar reaction of ni- gives derivatives which are normally high melting triles with formaldehyde was previously reported solids. Of special interest is the reaction of formby Hepp,2 but no yields were given and the scope aldehyde and acrylonitrile which yields methyleneand mechanism of the reaction were not examined bis-acrylamide, a useful monomer for vinyl polycritically. merization. The methylene-bis-amides prepared in the course of this investigation are reported in Table I. In the early experiments chloroform and cyclohexane were used as solvents for the nitrileR-C-NH-CH2-NH-C-R aldehyde mixture. In subsequent preparations the II II procedure was simplified by adding the mixture or 0 0 solution of reactants to 85% sulfuric acid which acts This reaction of nitriles and aldehydes which has both as a catalyst and a solvent. This latter probeen used only occasionally since its d i s c 0 v e r y 3 ~ ~cedure ~ ~ ensures a homogeneous system for the entire has been reinvestigated since i t provides a novel course of the reaction and leads to improved yields. Although i t might appear that the reaction inmethod for the preparation of polyamides in acid solution a t room temperature. Polyamides de- volves hydrolysis of the nitrile to an amide with the rived from the reaction of dinitriles with formalde- subsequent reaction of two moles of the amide with hyde are described in the following paper of this one mole of formaldehyde to form a rnethylene-bisamide,' this is not the case, since (a) amides do not series.6 The reaction of nitriles with formaldehyde is exo- react with formaldehyde under the reaction condithermic and occurs a t room temperature with re- tions used for nitriles and (b) nitriles are not conmarkable ease to give high yields of methylene-bis- verted to amides by 85% sulfuric acid a t a rate amides (often over 90%). The reaction is effected comparable to the reaction of nitriles with formalby adding a mixture of nitrile and formaldehyde dehyde. The reaction of nitriles with formalde(preferably as trioxane which is soluble in most hyde appears to proceed by a carbonium ion mechliquid nitriles) to an excess of 85% sulfuric acid solu- anism and may be represented by the series of tion, keeping the temperature a t 30" by cooling. equations At the completion of the reaction (from 1 to t i (A) CHiO + H f HO-CHz+ hours), the reaction mixture is poured into an exin) HO-CH,' + R-C=N cess of ice and water. The methylene-bis-amides R-C +=N--CH201% are usually precipitated as water-insoluble solids (C) R-C+ZK-CH~OII R--C=I\;-CH2' which may be isolated in a high degree of purity by I filtration. OH The amidation reaction provides highest yields (D) R-C=h'-CH~+ + R-CFZN with formaldehyde but other aldehydes such as I ;icetaldehyde, butyraldehyde and chloral can be OH used to give compounds of the type R-CO-NHR-C=N--CH*--N=C +-R C(R')H-NH-CO-R where K' is CH3-, C 3 H r , I OH Cl,C--. /iltlehytles which contain hydrogen atoms of benzene derivatives with formaldehyde in 85%
i l ) Presented before t h e Division of Organic Cherni-try a t t h e April, lP50. Meeting nl 1 he American Chemical Society. After submitting the nianuscript t o t h e Journal. it was found t h a t bfowry and Ringwald had submitted a paper on the preparation of polyamides from azelaonitrile a n d formaldehyde, which deals w i t h the mechanism of the reaction of nitriles with formaldehyde: THISJOURNAL, 72, 4439 (1950). (2) Hepp a n d Spiess, Be?'., 9, 1421 (1876); Hepp, ibid., 10, 1649
(1877). (3) Thiesing, J . prakt Chenz., 121 44, 570 (1891). (4) B a t t a n d Woodcock, J. Chcm SOL., 2322 (l!J48) ( 5 ) K r a u t , A n n . , 268, 109 (1890). (6) Magat, Chandler, Faris, Reitti 73, 1031 (1931:.
.iiiii
%liqlJiiry, 'I'IIIS
J O U H S ~ I,
( E ) R-C=N-CH2--PU'=C+-R
I
+ Hz0
OH
R-C-NH-CHZ-NH-C-R
I/
+ H+
I/
0
0
Even though the reaction is represented by a cdrbonium ion mechanism i t is probable that sulfates Are formed as intermediate products. Evidence (7, XValker "Formaldehyilr Y , 1 0 4 4 p LOci
\
