Abstract

The kinetics of oxidation of Theobromine by alkaline permanganate at a constant ionic strength of 0.05mol/dm3was studied spectrophotometrically. The reaction between permanganate and theobromine in aqueous alkaline medium exhibits 2:1stoichiometry. The reaction is of first order in substrate concentration and fractional order with respect to concentration of both permanganate and alkali. The pH influence indicated that the oxidation is base catalyzed. The reaction rate was found to increase with increasing ionic strength and dielectric constant of the medium. The proposed reaction mechanism involves the formation of a 1:1 intermediate complex between theobromine and an alkalipermanganate species in a pre-equilibrium step, which was confirmed by both spectral and kinetic evidence. The complex decomposes slowly in a rate-determining step, resulting in the formation of free radical. The free radical generated reacts with another alkali permanganate species in a subsequent fast step to yield the final products, which were identified by spot test and spectral studies. The reaction constants involved in the different steps of the reaction mechanism were calculated. The activation parameters with respect to the slow step of the mechanism were determined.

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