Kinetics and mechanism of oxidation of iso-propyl mandelate by manganese(III) pyrophosphate

Abstract Kinetics of the oxidation of the iso-propyl mandelate by manganese(III) pyrophosphate has been studied. The reaction is first order in both ester and in manganese(III). The rate is proportional to the square of the concentration of hydrogen ion but it is inversely proportional to the concentration of free pyrophosphate in the solution. Addition of manganese(II) ions has no effect on the rate of reaction. The rate is also affected by the composition of the solvent, acetic acid-water mixture. The rate decreases with increase in the proportion of acetic acid in the solvent mixture. The heat of activation and entropy of activation have values 26.5 kcal mol −1 and + 19.0 e.u. respectively. A mechanism which is consistent with the observed rate laws and other experimental facts has been proposed.