Potential chlorofluorocarbon replacements: OH reaction rate constants between 250 and 315 K and infrared absorption spectra

Abstract

We measured the rate constant for reactions of the OH radical with several potential chlorofluorocarbon replacements over the temperature range 251–314 K using laser photolysis laser‐induced fluorescence techniques. The compounds studied and Arrhenius parameters determined from fits to the measured rate constants are as follows: CHF2OCHF2 (E 134), k(T) = (5.4 ± 3.5) × 10−13 cm3 s−1 exp [(−3.1 ± 0.4 kcal mol−1)/RT]; CF3CH2CF3 (FC 236fa), k(T) = (2.0 ± 1.0) × 10−14 cm3 s−1 exp [(−1.8 ± 0.3 kcal mol−1)/RT]; CF3CHFCHF2 (FC 236ea), k(T) = (2.0 ± 0.9) × 10−13 cm3 s−1 exp [(−2.0 ± 0.3 kcal mol−1)/RT]; and CF3CF2CH2F (FC 236cb), k(T)= (2.6 ± 1.6) × 10−13 cm3 s−1 exp [(−2.2 ± 0.4 kcal mol−1)/RT]. The measured activation energies (2–3 kcal mol−1) are consistent with a mechanism of H atom abstraction. The tropospheric lifetimes, estimated from the measured OH reaction rates, and measured integrated infrared absorption cross sections over the range 770 to 1430 cm−1 suggest that E 134 and FC 236fa may have significant global warming potential, while FC 236ea and FC 236cb do not.