CF3CFHO radical: Decomposition vs. reaction with O-2

Two puzzles are associated with reactions of the CF3CFHO alkoxy radical: fi rst, the ratio of A-factors for the reaction with O-2 and that for decompos ition is about 500 times greater than expected: second, decomposition is mo re flavored when the alkoxy radicals an produced by the reaction of peroxy radicals (RO2) with NO, compared to when they are produced by RO2 radical d isproportionation. Recent experimental evidence suggests that a major fract ion of the exothermicity of the reaction RO2+NO is deposited into vibration al excitation of the alkoxy radical product. A combined electronic structur e and kinetic modeling study has been conducted to examine these issues. Th e results reported here implicate the reaction with O-2 as responsible for the surprisingly large A-factor ratio. They also support the notion that si gnificant numbers of vibrationally excited CF3CFHO alkoxy radicals are prod uced in the reaction of peroxy radicals with NO and that the radicals subse quently decompose promptly on a nanosecond time scale.