Electron transfer reactions of halogenated aliphatic peroxyl radicals: measurement of absolute rate constants by pulse radiolysis

Abstract

The peroxyl radicals Cl₃COO·, Cl₂CHOO·, ClCH₂OO·, CH₃OO; ·OOCCl₂CO₂ ^–, ·OOCHClCO₂ ^–, ·OOCH₂CO₂ ^–, ·OOCF₂CO₂ ^–, and (CH₃)₂C(OH)CH₂OO· have been generated in aqueous alcohol solutions by pulse radiolysis using the Brunel and Hahn-Meitner accelerators. The absolute rate constants of the one-electron transfer reactions of related aliphatic peroxyl radicals with ascorbate, promethazine, phenol, and tyrosine have been found to increase with increasing substitution of chlorine atoms. For the reaction of the radical Cl₃CO₂· and promethazine, at pH 6, k 6.0 ± 0.4 × 10⁸ l mol^–1 s^–1 has been measured. For the analogous reaction of the radical ClCH₂O₂·, k 3.3 ± 0.2 × 10⁷ l mol^–1 S^–1 has been determined.