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Atmospheric chemistry of HFC-143a: Spectrokinetic investigation of the CF3CH2O2 radical, its reactions with NO and NO2, and the fate of CF3CH2O

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  • Nielsen, Ole John
  • Elisabeth Gamborg
  • Jens Sehested
  • Timothy J. Wellington
  • Michael D. Hurley

The ultraviolet absorption spectrum of CF3CH2O2 radicals, the kinetics of their self-reaction, and their reactions with NO and NO2 have been studied in the gas phase at 296 K using a pulse radiolysis technique. A long path-length Fourier transform infrared technique was used to study the fate of CF3CH2O radicals. Absorption cross sections were quantified over the wavelength range 220-300 nm. At 250 nm, σ(CF3CH2O2) = (2.73 ± 0.31) × 10-18 molecule-1. By monitoring the rate of NO2 formation, k4 = (1.2 ± 0.3) 10-11 cm3 molecule-1 s-1 was found for the reaction of CF3CH2O2 radical with NO. The reaction of CF3CH2O2 radicals with NO gives CF3CH2O radicals. In the atmosphere, >99.3% of the CF3CH2O radicals react with O2 to give CF3CHO. By monitoring the rate of NO2 decay, k5 = (5.8 ± 1.1) × 10-12 cm3 molecule-1 s-1 was found for the reaction of CF3CH2O2 radical with NO2. The results are discussed with respect to the atmospheric chemistry of CF3CH3 (HFC-143a). As a part of the present work, relative rate techniques were used to measure the following rate constants: (2.6 ± 0.7) × 10-12 and (2.0 ± 0.5) × 10-12 for the reaction of F atoms with CF3CH3, (5.5 ± 0.3) × 10-11 for the reaction of F atoms with CF3CH2OH, and (3.6 ± 0.2) × 10-17 for the reaction with Cl atoms with CF3CH3 (units of cm3 molecule-1 s-1).

OriginalsprogEngelsk
TidsskriftJournal of Physical Chemistry
Vol/bind98
Udgave nummer38
Sider (fra-til)9518-9525
Antal sider8
ISSN0022-3654
StatusUdgivet - 1 dec. 1994

ID: 228192276