Comparison of methanolysis of a series of p-benzyloxybenzoyl chlorides with that of benzoyl, p-phenoxybenzoyl, and p-methoxybenzoyl chlorides

Abstract

The kinetics of the methanolysis (solvolysis) of a series of p-benzyloxybenzoyl chlorides have been compared with values for benzoyl, p-methoxybenzoyl. and p-phenoxybenzoyl chloride. Small rate differences between benzoyl chloride and the other compounds stem from counterbalancing large changes in enthalpies and entropies of activation, ascribed to different degrees of S_N1 character in the reactions. Differences within the benzyloxy-series are ascribed to effects of substituents on the inductive effect of the benzene ring of the benzyloxy-group. Data have been analysed in terms of the Hammett equation. Values of σ for the p-benzyloxy-group were obtained from both kinetic and acidity measurements: both are considerably less than the literature value, which we regard as suspect. A coefficient of transmission of electronic effects across a p-benzyloxy-group was determined as 0.17.