[ C O N T R I B U T I O N FROM T H E D E P A R T N E N T O F C H E M I S T R Y , OKLAHOMA A G X C W L T U R A L AND 3XECHANICAL C O L L E G E ]
N-BESZYLAMIDES AS DERIVATIVES FOR IDESTIFYING THE ACYL GROUP I Y ESTERS1,' 0. C. DERMER
AXD
JACK ICIXG
Received December 14, 1942
The standard method of identifying the acyl group in esters, involving saponification, isolation of the acid or salt, and conversion to a derivative, is always time-consuming and occasionally fruitless. To obtain a derivative directly from an ester, Koelsch and Tenenbaum (1) and Hardy (2) have recommended adding the ester to the bromomagnesium salt of an arylamine, to produce the corresponding arylamide. Buehler and Mackenzie (3) carried out direct aminolysis of twelve esters with benzylamine, RCOOR'
+ CeHbCH2NH2
--+
RCOXHCH2CeHs
+ R'OH
but found the method unsatisfactory for esters of higher fatty acids and halogenated acids. Of these two procedures, that employing benzylamine has now been modified and considerably extended. Tests of six reasonably common high-boiling organic bases-benzylamine, dibenzylamine, cyclohexylamine, dicyclohexylamine, ethylenediamine, and phenylhydrazine (4)-with several esters proved benzylamine to be best in speed of reaction and ease of removal from the amide derivatives. This is in fair agreement with the findings of Smith and Adkins (5) on the relative reactivity of benzylamine in aminolyzing amides. The principal improvements made on the procedure of Buehler and Mackenzie are the use of no water as diluent and the employment of ammonium chloride as catalyst. The absence of water permits attainment of higher temperatures and ensures homogeneity of the reaction mixture, and substituted ammonium ions are known to catalyze aminolysis of esters (6). Esters of the higher alcohols, being less reactive, are not adequately aminolyzed by boiling for an hour with benzylamine. This difficulty may be met by longer heating or by subjecting such esters t o a preliminary methanolysis, which is itself quite rapid (7) and which produces methyl esters of comparatively high reactivity (8). Many of the N-benzylamides described in this paper were prepared by aminolysis of the acids rather than the esters, simply because the acids were already at hand. The authors know of no case in which an aminolyzable acid yields a non-reactive ester. On the other hand, reactivity of an ester does not guarantee that the free acid will aminolyze ; it may undergo decarboxylation, as p-nitrophenylacetic acid does. Table I includes all K-benzylamides prepared by the procedure described in 1 Presented before the Organic Division at the Buffalo Meeting of the American Chemical Society, September, 1942. 2 Based mainly on the M. S. thesis of Jack King, 1942. 168
169
IDENTIFICATION OF ACYL GROUPS
TABLE I MELTINGPOINTS OF N-BENZYLAMIDES OF CARBOXYLIC ACIDS MELTING POINT,
Oca
