Mechanistic applications of high performance liquid chromatography. Rate–product correlations for competing solvolysis and aminolysis of benzoyl chloride

Abstract

Rates and products for methanolysis of benzoyl chloride in the presence of m-nitroaniline (10^–4–10^–1M) are reported. There is a good correlation between the rate enhancement caused by the added amine and the formation of amide product. The aminolysis reaction is first order in added amine, and similar results are observed for o- and p-nitroanilines. The results demonstrate that the reactions of nitroanilines involve these amines as nucleophiles, not as base catalysts. The presence or absence of rate–product correlations is an established probe of reaction mechanism, which can be implemented conveniently and with good accuracy by reversed-phase high performance liquid chromatography. Many of the measurements of product compositions reported in this paper were made on the same very dilute solutions used to obtain the kinetic data conductimetrically. Such low concentrations of neutral nucleophiles minimised the medium effect on reactivity. Selectivity data for reactions of benzoyl chloride with o-nitroaniline and (i) methanol or (ii) water in aqueous acetone are also reported. It is shown that the selectivity [see equation (5)] is independent of the concentration of nitroaniline.