Abstract: The kinetics of iridium(III) catalyzed oxidation of isobutyl alcohol by cerium(III) in aqueous sulphuric acid medium has been investigated by titrimetric technique in the temperature range of 25～40 ℃.The reaction order of [Ce(IV)] was found to be unity and that in isobutyl alcohol to be positive fractional. It was found that the pseudo first order ([(CH3)2CHCH2OH] >> [Ce(IV)]) rate constants kobs increases with the increase of [Ir(III)] and [H＋],but decreases with the increase of [HSO4-].Under the protection of nitrogen the reaction system does not induce polymerization of acrylamide indicating no generation of free radicals. Formatoin of a dinuclear complex involving the oxidant, catalyst and the substrate before the rate-determining step has been proposed in the reaction mechanism, and the rate equation derived from the mechanism can explain all experimental observations. From the hydrogensulphate dependence, Ce(SO4)2＋ has been found as the kinetically active species. The pre-equilibrium constants, rate constants of the rate-determining step together with the parameters were evaluated.

Key words: Iridium(III) ion, Cerium(IV) ion, Isobutyl alcohol, Catalyst, Kinetics and mechanism