A Kinetic Study of Phase Transfer Catalyzed Benzylation of 2,4,6-Tribromophenol in Liquid-Liquid Two-Phase Solution

Abstract

Phase-transfer catalytic reactions of the derivatives of benzyl halide and 2,4,6-tribromophenol have been successfully carried out in an organic solvent=alkaline solution of KOH two-phase medium. The main purpose of this work is to study the effects of the leaving groups, orientations, and functional groups of the derivatives of benzyl halide on the reaction rate and the product yield. To identify the reaction rate in the organic phase, 2,4,6-tribromophenol is employed as the nucleophilic reagent under phase-transfer catalytic reaction. Reactions of aqueous phase and organic phase can be separately carried out to determine the reaction rate constants. Results obtained from the single organic-phase reaction are compared with those obtained from the two-phase phase transfer catalytic reaction. According to the experimental data, simplified models for representing the single-phase reaction and the two-phase reactions were proposed and derived. The reaction rate constants for the single-phase model (k s ) and the two-phase model (k T ) were compared to show their consistency. The kinetics of the reactions of the derivatives of benzyl halide and 2,4,6-tribromophenol were also studied. The effects of the leaving group, orientation, and functional group of the organic substrate on the reaction rate constant were also investigated in detail. A satisfactory explanation was arrived at to account for the experimental evidence.