Kinetics of potassium bromate oxidation of cobalt(III)-bound and unbound ɑ-hydroxy acids

Abstract

Potassium bromate {Br(V)}oxidation of pentaammnine-cobalt( III)-bound and unbound mandelic and lactic acids has been studied in 0.20 mol dm^-3 HClO₄ in 70% aq acetic acid in the presence of 0.010 mol dm^–3 Hg(OAc)₂. The reactions exhibit total second order kinetics - first order in each reactant. As both Co(III)-bound and unbound ɑ-hydroxy acids get oxidised at comparable rates, ligation of carboxylic acid to cobalt(III) centre does not exert any electrostatic influence on the seat of attack, possibly the ɑ-C-H bond. A suitable mechanism involving formation of a radical intermediate in a slow step from the bromate ester is suggested.