Kinetics and mechanism of the oxidation of formic and oxalic acids by quinolinium fluorochromate

Kinetics and mechanism of oxidation of formic and oxalic acids by quinolini um fluorochromate (QFC) have been studied in dimethylsulphoxide. The main p roduct of oxidation is carbon dioxide. The reaction is first-order with res pect to QFC. Michaelis-Menten type of kinetics were observed with respect t o the reductants. The reaction is acid-catalysed and the acid dependence ha s the form: k(obs) = a + b[H+]. The oxidation of alpha-deuterioformic acid exhibits a substantial primary kinetic isotope effect (k(H)/k(D) = 6.01 at 303 K). The reaction has been studied in nineteen different organic solvent s and the solvent effect has been analysed using Taft's and Swain's multipa rametric equations. The temperature dependence of the kinetic isotope effec t indicates the presence of a symmetrical cyclic transition state in the ra te-determining step. Suitable mechanisms have been proposed.