Electron spin resonance studies of the radicals formed from C-nitroso compounds and olefins. Part 2.—Reactions of fluoro-olefins with 2,4,6-trichloronitrosobenzene and with nitrosobenzene

Abstract

The dark reactions of a number of fluoro-olefins with 2,4,6-trichloronitrosobenzene and with nitrosobenzene have been investigated. The fluoro-olefins CF₂CFCl, CF₂CFBr, CF₂CFI and CF₂CCl₂ gave free radicals, but none were detected with CF₂CH₂, CF₂CFH, CF₂CFCF₃ or CFClCFCl. The temperature at which the reactions are allowed to occur is a critical factor in determining the type of radical produced: at least two radicals are formed for each olefin studied. A temperature-dependent e.s.r. spectrum was found for the reaction between CF₂CFBr and nitrosobenzene in iso-octane: activation parameters for the interconversion process of the radical PhN([grphic omitted])CF₂CFBr— about the CF₂—N(O) bond were found to be 21.8 ± 1.0 kJ mol^–1, 23.8 ± 1.1 kJ mol^–1 and 6.6 ± 0.6 J mol^–1 K^–1 for the free energy, enthalpy and entropy, respectively, at 298 K.

Similarly, a temperature-dependent spectrum was detected from the reaction of CF₂CFBr with 2,4,6-trichloronitrosobenzene in CFCl₃: the slow limit could not be reached but the enthalpy of activation for interconversion of the radical ArN(O)CF₂CFBr— was estimated to be 21 ± 5 kJ mol^–1.