Kinetics and mechanism of oxidation of formic and oxalic acids by tetrakis(pyridine) silver dichromate

Kinetics and mechanism of oxidation of formic and oxalic acids by tetrakis(pyridine) silver dichromate (TPSD) in DMSO have beer studied. The main product of oxidation is carbon dioxide. The reaction is first order each with respect to TPSD and the organic acids. The reaction is acid-catalysed and the acid dependence has the from k(obs) = a + b[H+]. The oxidation of alpha-deuterioformic acid exhibits a substantial primary kinetic isotope effect (k(H)/k(D) = 5.65 at 298 K). The reaction has been studied in nineteen different organic solvents and the solvent effect has been analysed using taft's and Swain's multiparametric equations. The temperature dependence of the kinetic isotope effect indicates the presence of a symmetrical cyclic transition state in the rate determining step. Suitable mechanisms have been proposed.