NASA - National Aeronautics and Space Administration

The rate constants for the reactions of OH radicals with the fluorinated alkenes containing one Br atom (CFBr=CF₂, CHBr=CF₂, CH₂=CBr-CF₃, CH₂=CBr-CF₂-CF₃, and CH₂=CH-CF₂-CF₂Br), as well as CF₂=CF₂, were measured using the flash photolysis resonance fluorescence technique over the temperature range 250-370 K to give the following Arrhenius expressions: k_C2F3Br(T) = (2.02 ± 0.12)×10^-12×exp{(396 ±18)/T} cm³molecule^-1s^-1; k_C2HF2Br(T) = (1.30 +0.22/-0.18)×10^-12×exp{(370 ± 47)/T} cm³molecule^-1s^-1;
k_C3H2F3Br(T) = (1.36 +0.17/-0.14)×10^-12×exp{(317 ± 34)/T} cm³molecule^-1s^-1; k_C4H2F5Br(T) = (0.98 +0.35/-0.26)×10^-12×exp{(369 ± 90)/T} cm³molecule^-1s^-1; k_C4H3F4Br(T) = (0.85 +0.15/-0.12)×10^-12×exp{(201 ± 46)/T} cm³molecule^-1s^-1; k_C2F4(T) = (3.39 +0.22/-0.12)×10^-12×exp{(323 ± 11)/T} cm³molecule^-1s^-1. Ultraviolet absorption spectra of these brominated fluoroalkanes and bromoethene were measured between 164 and 276 nm. On the basis of these results, the atmospheric lifetimes were estimated to be 1.4, 2.4, 2.8, 3.2, 7.0, and 1.1 days, respectively. The general pattern of halolalkene reactivity toward OH is discussed.