Antioxidant Chemistry: Hypotaurine−Taurine Oxidation by Chlorite

Extensive experimental data have been collected on the oxidation of hypotaurine, H 2 NCH 2 CH 2 SO 2 H, by chlorite and chlorine dioxide. Hypotaurine is stable and reacts slowly with chlorite to give taurine, hypotaurine sulfonic acid, and monochloro- and dichlorotaurine. However, it reacts rapidly with chlorine dioxide with a second-order rate constant of 801 M -1 s -1 to give taurine. Oxidation occurs simultaneously at the sulfur center (to give the sulfonic acid) and at the nitrogen center (to give the chloramines). The stoichiometry of the reaction was experimentally determined to be ClO 2 - + H 2 NCH 2 CH 2 SO 2 H + H + → ClHNCH 2 CH 2 SO 3 H + H 2 O. The formation of dichlorotaurine is favored only in high acid environments.