Kinetics and mechanism of the oxidation of some α-hydroxy acids by quinolinium bromochromate

Abstract

The oxidation of glycollic, lactic, malic and a few substituted mandelic acids by quinolinium bromochromate (QBC) in dimethylsulfoxide (DMSO) leads to the formation of the corresponding oxoacids. The reaction is first order each in QBC and the hydroxy acids. The reaction is catalyzed by the hydrogen ions. The hydrogen ion dependence has the form k o b s = a + b [II + ]. Oxidation of mandelic acid has been studied in different organic solvents. The solvent effect has been analyzed by using Kamlet's and Swain's multiparametric equations. A mechanism involving a hydride ion transfer via a chromate ester is proposed.