Oxidation of l -Hydroxyproline by Aqueous Alkaline Permanganate--A Kinetic Study

The kinetics of oxidation of l -hydroxyproline in aqueous alkaline medium was studied spectrophotometrically. The reaction showed first order kinetics in permanganate ion concentration and an order less than unity in l -hydroxyproline and alkali concentrations. Increasing ionic strength and decreasing dielectric constant of the medium increase the rate. The oxidation reaction proceeds via an alkali-permanganate species which forms a complex with l -hydroxyproline. The latter decomposes slowly, followed by a fast reaction between a free radical of l -hydroxyproline and another molecule of permanganate to give the products. There is a good agreement between the observed and calculated rate constants under different experimental conditions. Investigations at different temperatures allowed the determination of the activation parameters with respect to the slow step of the proposed mechanism.