Oxidation of a Dipeptide by Electrolytically Generated Manganese(III) in Aqueous Sulfuric Acid Medium: A Kinetic and Mechanistic Study

Article abstract of DOI:10.1246/bcsj.69.41

The kinetics of oxidation of the simplest dipeptide, glycylglycine (GG) by electrolytically generated manganese^III-sulfate in aqueous sulfuric acid has been studied. The rate shows first order dependence on [Mn^III] and a fractional order each on [GG] and [H⁺]. The reduced product, Mn^II has no significant effect on the rate. An increase in ionic strength or decrease in dielectric constant of the medium increases the rate, while addition of complexing agents such as Cl^-, F^-, and P₂O₇^4- decreases the rate. A Michaelis-Menten type mechanism has been suggested to explain the results. The coefficient of the rate-determining step has been evaluated as a function of temperature, by measuring the rates at different temperatures. The corresponding activation parameters have also been computed. Evidence for transient existence of a free radical reaction intermediate has been given. The kinetics of oxidation of GG have also been compared with those of the monomer amino acid, glycine.