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 SN1 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.