Surendra N. Mahapatro

Kinetics and mechanism of chromic acid oxidation of lactic acid

Abstract The chromic acid oxidation of lactic acid (LA) has the rate expression - dCr(VI)/dt= [Cr(VI)][LA](k 1 +k 2 [H + ]+k 3 [LA]). Both the first order and second order reactions are two electron oxidations giving pyruvic acid. There is insignificant C-C cleavage.

Oxidation of hemoglobin by arenediazonium salts. The influence of dioxygen

Abstract The reactions of human hemoglobin with p-nitro- and p-chlorobenzenediazonium tetrafluoroborates in the presence and absence of molecular oxygen have been investigated in kinetic detail. The oxidation of iron(II) occurs with first order rate dependence on both the hemoglobin and diazonium salt concentrations, but inverse first order dependence on the concentration of molecular oxygen characterizes reactions performed in the presence of O 2 . In the absence of O 2 , nitrobenzene is the only product observed from hemoglobin oxidation by p-NO 2 C 6 H 4 N 2 + BF 4 − , and a 1:1 stoichiometry exists between nitrobenzene produced and Fe(II) oxidized. In the presence of O 2 , p-nitrophenol is the dominant product, but product yield is dependent on the ratio of reactants. Electron transfer to the diazonium salt rather than its corresponding diazohydroxide or diazoate is inferred from the relative absence of pH dependence on the rate of oxidation. The composite results are consistent with a mechanism for hemoglobin oxidation that requires molecular oxygen dissociation from oxyhemoglobin prior to oxidation by the diazonium salt. Implications of this investigation for the mechanism of arylhydrazine reactions with hemoglobin are discussed.

Peroxomonophosphoric acid oxidations: kinetics and mechanism of oxidation of aliphatic aldehydes

The peroxomonophosphoric acid (PMPA) oxidation of six aliphatic aldehydes has been studied in the pH range 0–13. The reactions are second order, first order each in [aldehyde] and [PMPA] at constant pH. In alkaline medium the stoicheiometric ratio of PMPA to aldehyde is 1.0. In acid medium the ratio is significantly higher (1.5) pointing to the fact that an oxidation reaction and a carbonyl-assisted decomposition of PMPA occur simultaneously through a common intermediate. The pH–rate dependence was complex. A suitable rate law in a limited pH range 0–3 has been derived.