Kinetics and mechanism of the oxidation of substituted malonic acids by the hexachloroiridate(IV) ion

Abstract

The kinetics of oxidation of malonic acid (H₂mal) and its n-butyl (H₂bmal), benzyl (H₂bzmal), and phenyl (H₂pmal) derivatives by hexachloroiridate(IV) ion have been studied at ionic strength 0.50 mol dm^–3 and at various temperatures, over a wide acidity range. The reactions are first order with respect to the concentrations of the oxidant and the reducing agents. The rates are enhanced by a decrease in the hydrogen-ion concentration, and are sensitive to the substituent group, increasing in the order H₂mal < H₂bmal < H₂bzmal < H₂pmal. A reaction mechanism is proposed and discussed. The first dissociation constant of the dicarboxylic acids and the corresponding thermodynamic parameters have also been obtained kinetically.