Fate of the radical anion of perfluoroaromatic compounds in aqueous solution. A pulse radiolysis study

Abstract

Hydrated electrons react with substituted perfluorinated aromatic compounds with diffusion controlled rate constants. For substituents with Hammett constant σ p < 0.06, the radical anions formed very rapidly loses F −. The phenyl radical formed undergoes, in the presence of an electron donating substituent, rapid intramolecular electron transfer and protonation on a ring carbon to yield radical cation or its conjugate base. Radical anions were observed on reduction of pentafluoroacetophenone (PFA) and pentafluoronitrobenzene (PFN). Evidence for the formation of the radical anion was obtained from observation of intermolecular electron transfer from PFA· − or PFN· − to p-benzoquinone (Q), methyl viologen (MV 2+) and anthraquinone-2-sulfonate (AQS −) to form Q· −, MV· + and AQS· −−. The rate constants for fluoride elimination are (7 ± 3) × 10 3 and (1 ± 0.5) × 10 3 s −1 for PFA· − and PFN· −, respectively.