Abstract
The osmium (VIII) (Os(VIII)) catalysed oxidation of thiamine (TA) by diperiodatocuprate (III) (DPC) in aqueous alkaline medium at a constant ionic strength of 0.18 mol dm -3 was investigated spectrophotometrically. 1:3 stoichiometry (thaimine:DPC) exhibited between the reaction of thiamine and DPC was observed in aqueous alkaline medium. The orders of the reaction with respect to [DPC], [Os(VIII)] and [thiamine] were unity, unity and less than unity respectively, in the concentrations range studied. The rate of the reaction increased as the concentration of alkali increased and periodate had retarding effect on the rate of reaction. Ionic strength had a negligible effect on the reaction rate. The main reaction products were identified by spot test and spectroscopic analysis. A mechanism involving reaction paths via free radical was proposed. The activation parameters for the slow step of the mechanism and also the thermodynamic quantities for different steps of mechanism were determined and discussed.
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