The kinetics of the oxidation of three biological thiols (l-cysteine, glutathione, and dl- penicillamine) to their sulfinic and sulfonic acid derivatives by CrOO2+ in aqueous perchloric acid and in the presence of 2-propanol have been studied spectrophotometrically with the aid of the initial-rates method. The kinetic order of the oxidant is 2, whereas that of the reductant is not defined. The acidity of the medium has a slight effect on the initial rates ( ...