A Kinetic and Mechanistic Study of Ir (III) Catalyzed Oxidation of Methionine by HCF (III) in aqueous alkaline medium medium

Abstract

Abstract The kinetic Study of Ir (III) chloride catalyzed oxidation of Methionine by hexacyanoferrate (abbreviated as HCF) III ions in aqueous alkaline medium has been investigated spectrophotometrically at constant ionic strength of 0.5 mol dm-3 and temperature 35 ± 0.1●C. The reaction rate shows first order kinetics with respect to [HCF (III)], [OH-] and [IrCl3]. The order of reaction is also first with respect to [Substrate] at its lower concentration tending towards zero at higher concentration. The ionic strength of the reaction mixture shows positive salt effect on the reaction rate. Different activation parameters were also evaluated by studying the reaction at four different temperatures. The stoichiometry of the reaction corresponds to a reaction in which one mole of the amino acid reacts with four moles of HCF (III) ions. Methionine sulphone was found to be the main product of oxidation was identified using an organic solvent method and IR Spectroscopy. A suitable mechanism has been proposed to explain all the experimental results. It is assumed that reaction proceeds through complex formation between substrate (abbreviated) and iridium trichloride. A rate law has been derived which verifies the results. CH3 –S-(CH2)2-CH (NH2) – COO− + 4HCF (III) Ir(III),H2O → CH3-SO2-(CH2)2-CH (NH2)-COO− + 4HCF (II)