ROLE OF EXCITED CF3CFHO RADICALS IN THE ATMOSPHERIC CHEMISTRY OF HFC-134A

The atmospheric degradation of HFC-134a (CF3CFH2) proceeds via the for mation of CF3CFHO radicals, Long path length FTIR environmental chambe r techniques were used to study the atmospheric fate of CF3CFHO radica ls. Two competing reaction pathways were identified for CF3CFHO radica ls: reaction with Oz, CF3CFHO + O-2 --> CF3C(O)F + HO2, and decomposit ion via C-C bond scission, CF3CFHO + M --> CS3 + HC(O)F + M. CF3CFHO r adicals were produced by two different reactions: either via the self- reaction of CF3CFHO2 radicals or via the CF3CFHO2 + NO reaction. It wa s found that decomposition was much more important when CF3CFHO radica ls were produced via the CF3CFHO2 + NO reaction than when they were pr oduced via the self-reaction of CF3CFHO2 radicals. We ascribe this obs ervation to the formation of vibrationally excited CF3CFHO radicals i n the CF3CFHO2 + NO reaction. Rapid decomposition of CF3CFHO radicals limits the formation of CF3C(O)F and hence CF3COOH in the atmospheric degradation of HFC-134a. We estimate that the CF3COOH yield from atmo spheric oxidation of HFC-134a is 7-20%. Vibrationally excited alkoxy r adicals may play an important role in the atmospheric chemistry of oth er organic compounds.