A kinetic and mechanistic study on the oxidation of arginine and lysine by hexacyanoferrate (III) catalysed by iridium (III) in aqueous alkaline medium

摘要

The kinetics of Ir (III) catalysed oxidation of some amino acids like arginine and lysine by hexacyanoferrate (abbreviated as HCF) (III) ions in aqueous alkaline medium at constant ionic strength 0.5 mol dm-3and temperature 35ºC has been studied spectrophotometrically. The reactions exhibit 2:1 stoichiometry and follow first order kinetics in [HCF (III)] and [alkali]. The dependence of the rate on substrate concentration has been found to be of Michaelis-Menten type. The ionic strength of the reaction mixture shows positive salt effect on the reaction rate. To calculate thermodynamic parameters, the reactions have been studied at four different temperatures between 35 to 50ºC. A complex mechanism involving the complex formation between catalyst and the substrate has been proposed. Keto acids;e- guanidino-α-oxovaleric acid and 6–amino-α-oxocaproic acid have been identified chromatographically and spectroscopically as the final product of oxidation of arginine and lysine, respectively. Based on the kinetic data and product analysis a reaction mechanism is proposed.