A study of the ruthenium(III) catalysed oxidation of L-phenylalanine by heptavalent manganese - A kinetic and mechanistic approach

The kinetics of the ruthenium(III) catalysed oxidation of L-phenylalanine by alkaline permanganate has been studied spectrophotometrically using a rapid kinetic accessory. The reaction is first order each in [oxidant] and [catalyst] with an apparent less than unit order each in [substrate] and [alkali] respectively. The results suggest the formation of a complex between the phenylalanine 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 and the activation parameters have been calculated. There is a good agreement between observed and calculated rate constants under different experimental conditions.