KINETICS AND MECHANISM OF THE OXIDATION OF SOME HYDROXYACIDS BY PYRIDINIUM FLUOROCHROMATE

Oxidation of glycolic, lactic and mandelic acids by pyridinium fluorochromate (PFC) leads to the formation of the corresponding oxoacids. The reaction is first order with respect to PFC. Michaelis-Menten type kinetics were observed with respect to the hydroxy acid. The values of the formation constants of the hydroxy acid-PFC complexes and the rates of their decomposition, at different temperatures, have been evaluated. Thermodynamic parameters of the complex formation and activation parameters for the decomposition of the complexes have been calculated. The oxidation of mandelic acid has been studied in 19 different organic solvents. Analysis of the solvent effect indicates that the cation-solvating power of the solvents plays the major role in reaction rate. Oxidation of alpha-deuteriomandelic acid indicates the presence of a primary kinetic isotope effect. The analysis of the dependence of kinetic isotope effect on temperature indicates that the reaction involves a symmetrical cyclic transition state. A suitable mechanism has been proposed.