593. Kinetics and mechanism of oxidation of mandelic, DL-malic, and lactic acid by ceric sulphate

Abstract

The mechanism proposed by Waters for the oxidation of a-hydroxy-acids by manganic pyrophosphate accounts for the kinetics of oxidation of mandelic, DL-malic, and lactic acid by ceric sulphate. The reactants pass through a cyclic transition state involving the hydroxy-acid and cerium(1v). It is suggested that the reactive species of cerium is Ce(SO,), and that the HSO,ion plays the r61e of an active inhibitor by forming H,Ce(SO,),Z-on reacting with the sulphate.

Manganese(II) catalysed oxidation of glycerol by cerium(IV) in aqueous sulphuric acid medium: a kinetic and mechanistic study

“…If the rate is inversely dependent on the HSO 4 -ion concentration, the overall effect of adding sulphuric acid would be to lower the rate ( Table 2). Similar behaviour has been reported in the oxidation of antimony(III) [11], mandelic acid [21,22], malic acid [23], fructose [24] and L-glutamic acid [25] by cerium(IV). Added cerium(III) is thought to retard the rate due to the formation of Ce 4?…”

“…The reaction is first order with respect to cerium(IV) and manganese(II) concentrations, and the order with respect to glycerol varies from first to zero order. Increasing sulphuric acid concentration results in a decrease in rate, this may be due to the formation [21] of an active inhibitor H 2 Ce(SO 4 ) 2 2-. The order with respect to H ?…”

Kinetics of cerium (IV) oxidation of mandelic acid. Ionic strength and specific cation effects

“…The first series of our experiments concerns the kinetics of oxidation in solution containing sulfuric acid alone (Table I) over an acid concentration range wider than that used previously by other investigators [3,4] 'rABLE I. Kinetic data obtained in solutions containing sulfuric acid alone (t = 25.0"C).…”

Kinetics and mechanism of the oxidation of a ferrous complex with an α,α′-diimine chelate ligand by ceric sulfate in aqueous acidic medium by UV-vis absorption spectroscopy

“…Results (Table 5 From earlier reports [18,19], it appears that, in aqueous sulfuric acid medium, cerium(IV) can exist in several forms, such as Ce 4+ In the oxidation of different substrates by cerium(IV) in aqueous sulfuric acid medium, one or more of the equilibria can be involved in the kinetics of the reaction and one or more of the species can be considered to be the reactive species of cerium(IV).…”

“…The excess of cerium(IV) is large, when all the specie, including active and inactive cerium(IV) specie, are present at significant concentrations [18,19] (20) and the reaction rate is inhibited by ceric sulfate at higher concentrations. For kƍ obs , the excess of sulfate ions is very large, and should be linear with a positive slope equal to K d /k K 1 , and a yintercept of 1/k.…”