A Comparative Kinetic Study of lridium(III) Catalysis in H2SO4 and HClO4 Media in the Cerium(IV) Oxidation of Diacetone Alcohol

Department of Chemistry, Osmania University, Hyderabad-500 007
Manuscript received 26 February 1985, revised 8 October 1985, accepted 9 March 1987

A study of Ir^III catalysed oxidation of diacetone alcohol (DAA) by Ce^IV in H2SO₄ and HCIO₄ media was undertaken to understand the mechanism of catalysis. The change in reactive species of Ce^IV in tnese media produces a marked effect on the relative rates of catalysed and uncatalysed reactions. The catalysis was found to be more pronounced in H₂SO₄ medium. The order in [Cu^IV] was found to be unity and that in [Ir^III] fractional in both the media studied. The order in [substrate] changed from unity in the uncatalysed reaction to fractional in the catalysed reaction in H₂SO₄ medium However, in HCl₄ medium, the order in [DAA] was found to be fractional both in Latabsed as well as uncatalysed reaction. A mechanism involving formation of Ir^III-DAA complex in a fast step followed by its reaction with Ce^IV in the slow step to give [Ir^IV complex] which decomposes to give lull and first stage intermediate products is proposed to explain the kinetic data.