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Kinetic and Mechanism of Ruthenium (III) Catalyzed Oxidation of 4-(3-Hydroxy Phenyl Amino)-4-Oxo Butanoic Acid by Hexacyanoferrate (III) in Aqueous Alkaline Medium

B. C. Sateesh, Vidyavati A. Shastry, S. Shashidhar and K. E. Manoj Kumar

The kinetics and mechanism of hexacyanoferrate (HCF(III)) oxidation of 4-(3-hydroxy phenyl amino)-4-oxo butanoic acid (4-Oxo acid) in aqueous alkaline medium has been studied at 26 ± 0.1 o C in presence of ruthenium (III) catalyst. The reaction shows first order dependence in each [HCF (III)] and [Ru (III)], zero order dependence in [4-Oxo acid] and fractional order dependence in [OH − ]. Variation of ionic strength by the addition of KNO 3 has no significant effect on the rate. The stoichiometry of the reaction is found to be 1:4 and the main oxidative products are N-(4-hydroxyphenyl) formamide and malonic acid. A mechanism involving formation of complex has been proposed and the active species of ruthenium (III) is understood as [Ru(H 2 O) 5 (OH)] 2+ . The reaction constants involved in the different steps of mechanism are calculated. Activation parameters with respect to slow st ep of the mechanism are calculated and tabulated. The rate constant of catalyzed reaction is found to be 0.184 × 10 − 2 s − 1 .