Studies on Mn(II)-catalyzed oxidation of α-amino acids by peroxomonosulphate in alkaline medium-deamination and decarboxylation: A kinetic approach

The kinetics and mechanisms of Mn(II)-catalyzed oxidative decarboxylation of five structurally different amino acids: alanine, valine, leucine, phenyl alanine and 2-methyl alanine, by peroxomonosulphate (PMS) in alkaline medium were studied at 313 K with a constant ionic strength of 0.05 mol dm−3. Analysis of the kinetic results revealed that the rate of oxidation was first-order in [PMS], [amino acid], [Mn2+] and inverse first-order in [OH−]. The effects of added product, ionic strength and dielectric constant were investigated. The reaction was studied at different temperatures and the activation parameters were calculated. The main products were identified as the corresponding carbonyl compounds by IR and by gas chromatography–mass spectrometry (GC–MS). Manganese peroxide (MnO(O)) was proposed as the intermediate to explain the experimental observations. The isokinetic temperature was calculated as 346 K by applying Exner's criterion. Catalytic constants were calculated at 313 K and are tabulated.

Kinetics of oxidation of α-substituted amino acids by permonosulphate in alkaline medium revealed the formation of manganese peroxide (Mn(O2)) as an intermediate. The overall reactivity of amino acids for Mn2+-catalyzed oxidation was found to be in the order: alanine > valine > 2-methyl alanine > phenyl alanine > leucine. The possible rate equation for the oxidation kinetics was proposed.Figure optionsDownload as PowerPoint slide