Hydrogen abstraction from aromatic aldehydes by trifluoromethyl radicals

Abstract

Trifluoromethyl radicals produced by the photolysis of hexafluoroacetone have been generated in the presence of benzaldehyde and of pentafluorobenzaldehyde. A mechanism has been postulated to explain the variation in product yields with experimental parameters. From the rate data obtained at different temperatures the Arrhenius equations for the hydrogen abstraction reactions of trifluromethyl radicals from pentaflurobenzaldehyde and benzaldehyde are calculated to be k₅/k^½2₂=(2.24 ± 0.15)× 10⁵ exp (–8630 ± 400/RT) mol^–½ cm^z.frac32; s^–½, and k₅/k^½₂=(1.122 ± 0.12)× 10⁴ exp (–4600 ± 300/RT) mole^–½ cm^z.frac32; s^–½. respectively, where k₅ is the rate constant for the hydrogen abstraction reactions and k₂ is the rate constant for the recombination of trifluoromethyl radicals.