CF3CFHO• radical: Decomposition vs. reaction with O2

Two puzzles are associated with reactions of the CF3CFHO alkoxy radical: first, the ratio of A‐factors for the reaction with O2 and that for decomposition is about 500 times greater than expected; second, decomposition is more favored when the alkoxy radicals are produced by the reaction of peroxy radicals (RO2) with NO, compared to when they are produced by RO2 radical disproportionation. Recent experimental evidence suggests that a major fraction of the exothermicity of the reaction RO2+NO is deposited into vibrational excitation of the alkoxy radical product. A combined electronic structure and kinetic modeling study has been conducted to examine these issues. The results reported here implicate the reaction with O2 as responsible for the surprisingly large A‐factor ratio. They also support the notion that significant numbers of vibrationally excited CF3CFHO alkoxy radicals are produced in the reaction of peroxy radicals with NO and that the radicals subsequently decompose promptly on a nanosecond time scale.