SYNTHESIS AND KINETICS OF OXIDATION OF PHENYLALANYL-GLYCINE, ISOLEUCYL-GLYCINE, AND LEUCYL-GLYCINE WITH ANODICALLY GENERATED MANGANESE(III) SULFATE. A MECHANISTIC STUDY

Abstract

The kinetics of oxidation of dipeptides (DP), namely phenylalanyl-glycine (Phe-Gly), isoleucyl-glycine (Ile-Gly) and leucyl-glycine (Leu-Gly), by Mn(III) have been studied in the presence of sulfate ions in acidic solution at 26 °C. The reaction was followed spectrophotometrically at λ_max = 500 nm. A first-order dependence of the rate on both [Mn(III)] and [DP] was observed. The rate is independent of the concentration of reduction product, Mn(II) and hydrogen ions. The effects of varying the dielectric constant of the medium and addition of anions such as sulfate, chloride and perchlorate were studied. The activation parameters have been evaluated using Arrhenius and Eyring plots. The oxidation products were isolated and characterized. A mechanism involving the reaction of DP with Mn(III) in the rate limiting step is suggested.

ACKNOWLEDGMENT

One of the authors (K. S. R) is thankful to the University Grant Commission-Council of Science and Industria1 Research, New Delhi, for financial support. M. N. K. is thankful for the award of the University Project Junior Research Fellowship, University of Mysore.