Kinetics and mechanism of electron transfer reaction: Oxidation of sulfanilic acid by hexachloroiridate(IV) in acid medium

The kinetics of oxidation of sulfanilic acid by [IrCl6](2-) in acid medium has been studied. The reaction is overall second order being first order with respect to each reactant. However, rate is retarded by hydrogen ion concentration. Various proposals have been suggested on the basis of reactivity of Ir(IV) species. The activation parameters such as energy and entropy of activation calculated by Eyring equation are found to be 59.99 +/- 0.93 kJ mol(-1) and -106.44 +/- 2.2 J K-1 mal(-1) respectively. The oxidation product, 2-keto-azoxy- benzene-4,4'-disulfonic acid has been confirmed spectrally.