KINETICS AND MECHANISM OF THE OXIDATION OF SOME a-HYDROXY ACIDS BY QUINOLINIUM CHLOROCHROMATE

Abstract

Normal 0 The oxidation of glycollic, lactic, malic and a few substituted mandelic acids by quinolinium chlorochromate (QCC) in dimethylsulphoxide (DMSO) leads to the formation of corresponding oxoacids. The reaction is first order each in QCC. Michaelies-Menten type of kinetics is observed with respect to the hydroxy acids. Reaction is failed to induce the polymerisation of acrylonitrile. The oxidation of a ‑deuteriomandelic acid shows the presence of a primary kinetic isotope effect ( k H / k D = 5.75 at 298 K). The reaction does not exhibit the solvent isotope effect The reaction is catalysed by the hydrogen ions. The hydrogen ion dependence has the form: k obs = a + b [H + ]. Oxidation of p-methyl mandelic acid has been studied in 19 different organic solvents. The solvent effect has been analysed by using Kamlet’s and Swain’s multiparametric equations. A mechanism involving a hydride ion transfer via a chromate ester is proposed.