A SECONDARY REACTION IN THE OXIDATION OF L-METHIONINE BY CHROMIUM(VI)IN ACIDIC MEDIUM

The reaction mechanism of the oxidation Of L-methionine by chromium(VI ) in perchloric acid has been reviewed. Secondary reaction products fo rmed by methionine C(1)-C(2) bond scission were observed, besides the major oxidation product: methionine sulphoxide. Methionine sulphoxide and methional (3-[methylthio]-propionaldehyde) were found to be produc ed by two parallel redox steps. Ammonia and carbon dioxide have been i dentified and their yields determined. Free radicals were detected dur ing the reaction course and the yield of carbon dioxide was found to b e independent of the amount of free radical scavenger. When the amino group was blocked by an acetyl group the N-acetylmethionine sulphoxide was the only oxidation product. The mechanism with the associated rea ction kinetics are presented and discussed.