Kinetics and mechanism of the hydrolysis of 1-aryloxyethyl alkanoates

Abstract

The kinetics and mechanism of the hydrolysis of 1-aryloxyethyl alkanoates are reported. In acidic media, ¹⁸O isotope exchange studies, kinetics, activation parameters and substituent effects point clearly to an A_A1-1 mechanism with the formation of an alkoxycarbonium ion as the rate-limiting step. In basic media the data indicate a conventional B_AC-2 mechanism through attack of hydroxide ion on the carbonyl carbon. In neutral medium (pH 2.5–8.8) there is a certain amount of conflicting evidence which leads, however, to the proposal that hydrolysis occurs via attack of a water molecule on the acyl carbon as the rate-limiting step.