Palladium(II) Catalysed Oxidation of l-proline by Heptavalent Manganese in Aqueous Alkaline Medium: A Free Radical Intervention and Decarboxylation

The kinetics of palladium(II) catalysed oxidation of l-proline by permanganate in alkaline medium was studied spectrophotometrically. The reaction between permanganate and l-proline in alkaline medium exhibits 2:1 stoichiometry (KMnO₄: l-proline). The reaction is first order with respect to MnO₄⁻] and Pd(II)], an apparent less than unit order in alkali] and zero order in l-proline] under the experimental conditions. Reaction rate increases with increase in ionic strength and decrease in solvent polarity of the medium. Addition of reaction products did not affect the rate significantly. A mechanism involving the intervention of a free radical generated by l-proline has been proposed. The reaction constants involved in the mechanism were evaluated. The activation parameters with respect to the slow step of the Scheme were evaluated and are discussed.