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The CF 3 C(O)O 2 Radical. Its UV Spectrum, Self-Reaction Kinetics, and Reaction with NO

1996; American Chemical Society; Volume: 100; Issue: 11 Linguagem: Inglês

10.1021/jp9532935

1541-5740

M. Matti Maricq, Joseph J. Szente, Gregory A. Khitrov, Joseph S. Francisco,

Advanced Chemical Physics Studies

Flash photolysis combined with time-resolved UV spectroscopy and transient infrared absorption is used to investigate the reactions of CF3C(O)O2 with itself, CF3O2, and nitric oxide. The UV spectrum of CF3C(O)O2 exhibits two bands, the stronger short wavelength component of which has a maximum cross section of 7.1 × 10-18 cm2 at 207 nm. These bands are used to monitor the disappearance of CF3C(O)O2 and the secondary formation of CF3O2, yielding a self-reaction rate constant of × 10-12 e(270±200)/T cm3 s-1. The cross reaction between CF3C(O)O2 and CF3O2 is found to be slow, having a rate constant of ≤2 × 10-12 cm3 s-1. Transient IR monitoring of the loss of NO and concomitant formation of NO2 leads to a rate constant of × 10-12 e(563±115)/T cm3 s-1 for the reaction between CF3C(O)O2 and NO. This result implies that CF3C(O)O2 radicals formed as intermediates in the atmospheric degradation of hydrofluorocarbons (HFCs) are rapidly converted into CF3O2 radicals, which are in turn converted into carbonyl fluoride and FNO.