Kinetics and mechanism of osmium(VIII)-catalyzed oxidation of D-proline and L(–)-methionine by hexacyanoferrate(III)

The osmium(VIII)-catalyzed oxidation of D -proline and L (–)-methionine by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The reactions follow kinetics different from those of the oxidation of many amino acids investigated earlier, being first order in hexacyanoferrate(III) and osmium(VIII). The order in proline or methionine and OH^? decreases from unity to zero at higher concentrations of proline or methionine and OH^?, respectively. A mechanism consistent with the kinetic data is proposed and discussed.