Kinetics in phase-transfer catalysis: a theoretical study. Part 2. The method of initial rates

Abstract

A theoretical study of a phase-transfer-catalysed irreversible S_N2 reaction, RY + X^–→ RX + Y^–, was undertaken in order to establish the necessary conditions for the application of the method of initial rates in phase-transfer catalysis. The system studied consists of a slow chemical reaction coupled to a fast anion exchange via an organic quaternary 'onium salt. An error in measuring the initial reaction rate was shown to be inherent in a system in which the released anion Y^– is initially absent. This error is negligibly small when the selectivity extraction constant K_x/y^sel 1 for equal reactant concentrations and when K_x/y^sel 0.1 for a five-fold or more molar excess of concentration of the ionic reactant.