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Kinetics and Mechanism of Iridium (III) Catalyzed Oxidation of Some Amino Acids by Hexacyanoferrate (III) Ions in Aqueous Alkaline Medium

Anjali Goel, Shakunj and Shivani

The kinetics of oxidation of some amino acids like – alanine, valine and leucine by hexacyanoferrate (III) ions catalyzed by iridium (III) in aqueous alkaline medium at constant ionic strength and temperature has been studied spectrophotometrically. The results show that the reaction rates follow first order kinetics with respect to hexacyanoferrate (III), iridium (III) and hydroxide ions concentration in the oxidation of all the three amino acids. The dependence of rate on substrate concentration has been found first order at lower concentration, which tends to be zero order at higher concentration in the oxidation of all the three amino acids. The linear plots between log (-dc/dt) and μ suggest positive salt effect. Thermodynamic parameters were evaluated by studying the reactions at four different temperatures between 350C to 500C under pseudo first order conditions. 2 : 1 Stoichiometry was observed between hexacyanoferrate (III) and amino acids. From the results, it has been concluded that all the three amino acids show same kinetic behavior. Therefore, a common mechanism involving the formation of complex between catalyst and substrate has been suggested.