Kinetics and mechanism of reduction of hexachloroiridate (IV) by kojic acid in aqueous perchlorate solutions

The kinetics of kojic acid reduction of hexachloroiridate (IV) in aqueous perchlorate solutions at constant ionic strength of 1.0 mol dm(-3) has been investigated spectrophotometrically. The reaction showed a first-order dependence in [IrCl6](2-) and a fractional-order with respect to kojic acid concentration. Kinetic evidence for the formation of an intermediate complex via free-radical mechanism is presented. The results obtained indicate that increasing the [H+] is accompanied by an appreciable acceleration of the rate of reaction at pH's less than or equal to 0.4. The activation parameters have been evaluated and a tentative reaction mechanism consistent with the results is suggested.