Kinetic, Mechanistic, and Thermodynamic Investigations of Iridium (III) Catalyzed Oxidation of D-Mannitol by N-Chloro-P-Toluenesulfonamide in Perchloric Acid Medium

The present paper deals with the kinetics and mechanism of homogeneously Ir(III) chloride catalyzed oxidation of D-mannitol by chloramine-T [CAT] in perchloric acid medium in the temperature range of 30 to 45 °C. The reaction is carried out in the presence of mercuric acetate as a scavenger for chloride ion. The experimental results show first-order kinetics with respect to the oxidant [CAT] and catalyst [Ir(III)], while zero-order with respect to substrate, i.e., D-Mannitol was observed. The reaction shows negligible effect of [Hg(OAc)2], [H^+] and ionic strength of the medium. Chloride ion positively influences the rate of reaction. The reaction between chloramine-T and D-Mannitol in acid medium shows 2:1 stoichiometry. To calculate activation parameters, the reactions have been studied at four different temperatures between 30 to 45 °C. A mechanism involving the complex formation between catalyst and oxidant has been proposed. Mannonic acid has been identified chromatographically and spectroscopically as the final product of oxidation of D-Mannitol. Based on the kinetic data, reaction stoichiometry, and product analysis, a reaction mechanism has been proposed and rate law derived.