Ruthenium(III) catalysed oxidation of L-alanine by alkaline permanganate: A kinetic and mechanistic approach

The kinetics of the ruthenium(III) catalysed oxidation of L-alanine by alkaline permanganate was studied spectrophotometrically using a rapid kinetic accessory. The reaction is first order with respect to [oxidant] and [catalyst] with an apparent less than unit order in [substrate] and [alkali] respectively. The results suggest the formation of a complex between the alanine and the hydroxylated species of ruthenium(III). The complex reacts further with the alkaline permanganate species in a rate-determining step, resulting in the formation of a free radical, which again reacts with the alkaline permanganate species in a subsequent fast step to yield the products. The reaction constants involved in the mechanism were calculated. There is a good agreement between observed and calculated rate constants under different experimental conditions. The activation parameters with respect to slow step of the mechanism were calculated and discussed.