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

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(-3) and temperature 35 degrees C has been studied spectrophotometrically. The reactions exhibit 2 : 1 stoichiometry and follows first order kinetics in [HCF(III)] and [alkali]. The dependence of rate on substrate concentration has been found to be Michaelis-Menton type. The ionic strength of the reaction mixture shows positive salt effect on the reaction rate. To calculate thermodynamic parameters the reaction has been studied at four different temperatures between 35-50 degrees C. A complex mechanism involving the complex formation between catalyst and the substrate has been proposed. Keto acids-epsilon-guanidino-alpha-oxo valeric acid, 6-amino-alpha-oxo caproic acid have been identified as the final product of oxidation chromatographically and spectroscopically. Based on the kinetic data and product analysis a reaction mechanism is proposed.