A comparative study of quinolinium dichromate oxidation with hydrophobic dependence amino acids. A kinetic and mechanistic approach

A detailed study of kinetics is required to predict the susceptibility of amino acid residues towards metal-catalyzed oxidation. The effect of quinolinium dichromate on the oxidation of a set of amino acid residues with different hydrophobicity in HClO₄ medium at 25 °C has been fairly studied. The kinetics of the reaction was followed spectrophotometrically at λ_max = 440 nm. The reaction has unit dependence on each of the substrates, quinolinum dichromate and acid concentrations. The effect of dielectric constant of the medium on the rate was studied. The induced polymerization of acrylonitrile was observed. The oxidation products were isolated and characterized. Dependence of reaction rate on temperature has been studied and activation parameters were computed. A mechanism consistent with the observed results has been proposed. Of the four amino acid residues, proline is oxidized at a faster rate than all other amino acids. This may be due to the hydrophobic induced oxidation. Therefore, the overall order of amino acid sensitivity to oxidation was found to be Pro > Thr > Ser > Lys.