Electron transfer reactions of halothane-derived peroxyl free radicals, CF3CHClO2˙: measurement of absolute rate constants by pulse radiolysis

Abstract

The halothane-derived peroxyl radical CF₃CHClO₂˙ has been generated in aqueous solutions by pulse radiolysis. Absolute rate constants for the reduction of halothane (2-bromo-2-chloro-1,1,1-trifluorethane) by hydrated electrons, hydrogen atoms, and propan-2-ol free radicals have been determined to be k 1.4 × 10¹⁰,3.8 × 10⁸, and 7.6 × 10⁷ l mol^–1 s^–1, respectively. The predominant product radical CF₃ĊHCl rapidly adds O₂, and an estimate of k 1.3 × 10⁹ l mol^–1 s^–1, has been obtained for the absolute rate constant of this reaction. The resulting peroxyl radical CF₃CHClO₂˙ has been found to react rapidly with a variety of nucleophilic compounds such as 2,2′-azinobis(3-ethylbenzthiazoline-6-sulphonate), the phenothiazines promethazine, chlorpromazine, and metiazinic acid, the vitamins C and E, and propyl gallate. The absolute rate constants for these reactions are found to be generally lower than for corresponding reactions of the carbon tetrachloride-derived radical, CCl₃O₂˙.