Kinetics of ‘initial burst’ in the solid–liquid phase‐transfer catalysis. Nucleophilic substitution of 2‐octyl mesylate with potassium bromide

Abstract

The S N 2 substitution of 2-octyl mesylate with solid KBr under the conditions of phase-transfer catalysis was studied kinetically using the model approach of 'initial burst.' It is suggested that such kinetics reflect the contribution of mass transfer and surface poisoning. The proposed model is used to explain the influences of catalyst, solvent, stirring speed, activation and agitation effects. The mechanistic scheme suggests that the reaction is described by two separate kinetic stages, one of which reflects the intrinsic rate-limited step and the other the mass transfercontrolled step.

A Systematic Investigation of Quaternary Ammonium Ions as Asymmetric Phase-Transfer Catalysts. Synthesis of Catalyst Libraries and Evaluation of Catalyst Activity

“…This type of behavior has previously been reported as a function of ammonium counterion and is indicative of an interfacial mechanism. 40,77 The induction period was seen under the protocol wherein the base was added last. However, if the order of addition of reagents was changed such that the alkylating agent was added last, then the converse was observed and appearance of product was rapid at first, but quickly declined (a kinetic “burst”).…”