The ceric ion oxidation of mandelic acid and α-hydroxybutyric acid

Abstract

The oxidation of mandelic acid and α-hydroxybutyric acid by cerium(IV) in aqueous sulphuric acid solutions has been studied at several temperatures. The oxidation of mandelic acid is first-order with respect to both cerium(IV) and mandelic acid. The energy of activation is 18·9 ± 0·5 kcal.mole^–1, and the entropy of activation -0·3 ± 1 e.u. Initially, the oxidation of α-hydroxybutyric is first-order in cerium(IV) and organic acid, but it later deviates from the rate law in a manner which suggests successive slow steps between cerium(IV) and oxidation products of the acid. For the second-order portion, the activation parameters are E_a= 22·8 ± 9 kcal.mole^–1 and ΔS*= 4·8 ± 1.