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

Neha Vyas, Ajay Sharma, Amit Daiya, Anurag Choudhary, Monica Sharma, Vinita Sharma

Abstract


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 (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.


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DOI: http://dx.doi.org/10.17628/ecb.2013.2.859-865

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