The chromic acid oxidation of hydroxy acids—Catalysis by manganous ions

Kinetic data for the catalysis by manganese (II) of the chromic acid oxidation of α-hydroxy and α-keto acids over a range of Mn (II) concentrations are reported. A first order dependence on Mn(II) in the lower concentration regions with an upper limit is noticed. The results are explained on the basis of a slow rate determining decomposition of an Mn (III)—substrate complex which is formed by the oxidation of an Mn (II)—substrate species formed initially. The enhanced positive catalysis by Mn (II) in the case of Cr (VI) oxidation of pyruvic acid over that of lactic acid is attributed to an independent mechanistic path.