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Kinetics and Mechanism of the Oxidation of some Hydroxy Acids by Imidazolium Fluorochromate

D. Baghmar, P. Purohit, M. Baghmar, I. K. Sharma and Vinita Sharma

The oxidation of glycollic, lactic, malic and a few substituted mandelic acids by imidazolium fluorochromate (IFC) in dimethylsulphoxide (DMSO) leads to the formation of corresponding oxoacids. The reaction is first order each in IFC. Michaelies-Menten type of kinetics is observed with respect to the hydroxy acids. Reaction failed to induce the polymerisation of acrylonitrile. The oxidation of α-deuteriomandelic acid shows the presence of a primary kinetic isotope effect (kH/kD = 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: kobs = 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.