KINETICS AND MECHANISMS OF OXIDATION BY METAL-IONS .13. OSMIUM(VIII) CATALYZED OXIDATION OF CYCLOALKANOLS BY ALKALINE HEXACYANOFERRATE(III)

The kinetics of OsO4-catalysed oxidation of cyclopentanol, cyclohexanol and cyclooctanol by alkaline hexacyanoferrate(III) have been studied at low [OH-] so that the equilibrium between alcohol and alkoxide ion is not unduly shifted towards the latter. The reaction shows a first-order dependence in [OH-]. The order of the reaction with respect to cycloalcohol is fractional, indicating the formation of an intermediate complex with Os(VIII) since the order with respect to hexacyanoferrate(III) ion is zero. The order with respect to Os(VIII) may be expressed by the equation k(obs) = a + b[Os(VIII)]. The analysis of the rate data indicates a significant degree of complex formation between [OsO3(OH)3]- and ROH. It was found that the bimolecular rate constant k for the redox reaction between complex and OH- >> k1, the forward rate constant for the formation of alkoxide ion. The activation parameters of these rate constants are reported.