N‐bromosuccinimide oxidation of dipeptides and their amino acids: Synthesis,kinetics and mechanistic studies

Dipeptides (DP), namely valyl–glycine (Val–Gly), alanyl–proline (Ala–Pro), and valyl–proline (Val–Pro) were synthesized by classical solution phase methods and characterized. The kinetics of oxidation of amino acids (AA) and DP by N‐bromosuccinimide (NBS) was studied in the presence of perchlorate ions in acidic medium at 28°C. The reaction was followed spectrophotometrically at λ_max = 240 nm. The reactions follow identical kinetics, being first order each in NBS], AA], and DP]. No effect on H⁺], reduction product succinimide], and ionic strength was observed. Effects of varying dielectric constant of the medium and addition of anions such as chloride and perchlorate were studied. Activation parameters have been computed. The oxidation products of the reaction were isolated and characterized. The proposed mechanism is consistent with the experimental results. An apparent correlation was noted between the rate of oxidation of AA and DP. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 376–385, 2006