Atmospheric Chemistry of CF₃CFHCF₃ (HFC-227ea):  Spectrokinetic Investigation of the CF₃CFO₂•CF₃ Radical, Its Reactions with NO and NO₂, and Fate of the CF₃CFO•CF₃ Radical

The ultraviolet absorption spectrum of the CF3CFO2•CF3 radical, the kinetics of its self-reaction and reactions with NO and NO2 have been studied in the gas phase at 296K using a pulse radiolysis technique. A long-path-length Fourier transform infrared technique was used to study the fate of the CF3CFO•CF3 radical. Absorption cross sections for the CF3CFO2•CF3 radical were quantified over the wavelength range 220−270 nm. At 230 nm, σ(CF3CFO2•CF3) = (351 ± 73) × 10-20 cm2 molecule-1. The observed rate constant for the CF3CFO2•CF3 self-reaction was (1.8 ± 0.4) × 10-12 cm3 molecule-1 s-1. The rate constants for the reaction of CF3CFO2•CF3 radicals with NO and NO2 were k3 = (2.1 ± 0.9) × 10-11 and k4 = (4.8 ± 1.4) × 10-12 cm3 molecule-1 s-1. The atmospheric fate of CF3CFO•CF3 radicals is decomposition via C−C bond scission to give CF3 radicals and CF3C(O)F. In 1000 mbar of SF6 at 296 K decomposition of CF3CFO•CF3 radicals proceeds at a rate greater than 1 × 105 s-1. As part of this work relative rate techniques were used to measure k(Cl+CF3CFHCF3) = (4.5 ± 1.2) × 10-17 and k(F+CF3CFHCF3) = (1.5 ± 0.5) × 10-13 cm3 molecule-1 s-1. This compares well with the value of k(F+CF3CFHCF3) = (1.9 ± 0.4) × 10-13 cm3 molecule-1 s-1 obtained by pulse radiolysis. The results are discussed in the context of the atmospheric chemistry of HFC-227ea.