Abstract
The catalytic activities of 2,2′-bipyridyl (bipy) and oxalic acid (Oxa) in the HCrO4– oxidation of some substituted trans-cinnamic acids have been investigated in acidic solutions. The Cr(VI)–bipy and Cr(VI)–Oxa complexes are believed to be the probable reactive electrophiles in this redox process. The kinetic data reveal that electron-releasing groups enhance the reactivity to a significant extent while the electron-withdrawing ones reduce the rate marginally. It appears that the mechanism of bipy/Oxa catalysed chromium(VI) oxidation of unsaturated systems to the corresponding cleavage products involves an electrophilic attack of the reactive complex at the C–C double bond. The formation of a ternary complex as an intermediate is envisaged to describe the redox process. In this paper, we also report on the kinetic form of the oxidation of trans-stilbene to methyl 3-hydroxy-2,3-diphenylpropanoate. The mechanistic pathway has been determined based on the kinetic behaviour and the product assignment.