Kinetics and mechanism of oxidation of D-glucose by tetraethylammonium chlorochromate in aqueous acetic acid

In an attempt for developing new oxochromium(VI) reagents for effective and selective oxidation of organic substrates under mild conditions we report in the present paper the kinetic and mechanistic study of the oxidation of D-glucose by tetraethylammonium chlorochromate (C2H5)(4)NCrO3Cl. The reaction has been carried out in aqueous acetic acid 50% (v/v) medium in the presence of perchloric acid at constant ionic strength. The reaction has been found to be first order with respect to each of the oxidant and substrate under pseudo-first order conditions. The reaction is catalysed by acid and follows a first order dependence on H+ ion concentration. The ionic strength variation has no effect on the reaction rate. The decrease in dielectric constant of the medium increases the rate of reaction. An 1:1 stoichiometry is observed in the oxidation and the reaction rate is not retarded by the addition of radical trapping agent acrylonitrile. The effect of temperature is studied and the various activation parameters are determined. The products of oxidation are identified to be arabinose and formic acid. On the observed facts, a hydride ion transfer mechanism is proposed.