On the Reactions of Thiols, Sulfenic Acids, and Sulfinic Acids with Hydrogen Peroxide

The reaction of thiols with H2O2 is central to many processes essential to life, from protein folding to redox signaling. The initial products are assumed to be sulfenic acids, but their observation, and the kinetic and mechanistic characterization of their subsequent reactions, has proven challenging. The introduction of a 9-fluorotriptycene substituent enabled the use of F-19 NMR to directly monitor the reaction of a thiol with H2O2 to yield a sulfenic acid, and its subsequent oxidation to sulfinic and sulfonic acids. The oxidations are specific base catalyzed, as revealed by the lack of isotope effects and the dependence of the kinetics on pH but not buffer concentration.