Kinetics and mechanism of rhodium(III)-catalysed oxidation of 1,2-glycols by acid bromate

Summary Rh^III-catalysed oxidation of 1,2-glycols by acid bromate was studied in the presence of Hg(OAc)₂ at 40°C. The order is zero with respect to [BrO₃^–] and unity in [Rh^III] and in [glycol]. The oxidation rate is unaffected by variation in [H⁺] and added salts. Stoichiometric studies indicate that one mole of bromate consumes three moles of glycol giving the corresponding carbonyl compounds. A suitable mechanism involving direct reaction between Rh^III and glycol to give product,via hydride ion abstraction by Rh^III, is proposed.