Kinetics and Mechanism of Electron Transfer Reactions of Aquo-thallium(III) with Hexitols in Acid Perchlorate Medium

Chemistry Department, Holkar Science College, lndore-452 001
Manuscript received 30 November 1992, revised 12 July 1993, accepted 1 September 1993

The kinetics of electron transfer reactions of aquo-thallium(III) with o-mannitol, o-glucitol and o-galactitol have been investigated under the pseudo-first order conditions. The variation of rate constant with hexitol concentration suggests the formation of an intermediate complex prior to the rate-determining step of its disproportionation. The rate decreases with increase in acidity, and is strongly inhibited by complexing chloride and acetate ions. Equilibrium constants of the complex formation between thallium(III) and acetic acid, chloro acetic acid and propionic acid have been computed from the observed retardation in rate of the electron transfer reaction of thallium(lll) with D-mannitol by these complexing monocarboxylic acids. Corresponding aldohexoses have been confirmed as initial reaction products. Free radical formation has been confirmed by the induced polymerisation reaction with acrylnitrile and also by the epr spin trapping technique. Rate law has been derived from the proposed mechanistic steps to explain the kinetic and other results of this study.