NASA - National Aeronautics and Space Administration

The rate constants for the reactions of OH radicals with the fluorinated ethers, CHF₂-O-CHF₂ (HFOC-134) and CF₃CH₂-O-CH₂CF₃ (HFOC-356mff), were measured using the flash photolysis resonance fluorescence technique over the temperature range 277-370 K to give the following Arrhenius expressions: k_HFOC-134(T) = (0.63 +0.20/-0.16)×0^-12×exp{-(1646±76)/T} cm³molecule^-1s^-1, k_HFOC-356mff(T) = (2.32 +0.46/-0.41 )×10^-12  ×exp{-(790 ± 47)/T} cm³molecule^-1s^-1 . On the basis of the analysis of the available experimental results, the following Arrhenius expression can be recommended for the rate constant of the reaction between OH and HFOC-134: k_HFOC-134(T) = (0.82 +0.34/-0.24)×10^-12×exp{-(1730 ± 110)/T} cm³molecule^-1s^-1. Atmospheric lifetimes were estimated to be 24.8 years for HFOC-134 (23.8 years based on the results of this study alone) and 0.3 years for HFOC-356mff. Infrared absorption cross sections of HFOC-134, HFOC-356mff, and HFOC-125 (CHF₂-O-CF₃) were measured at T ) 295 K from 500 to 1600 cm^-1 and the global warming potentials of the three compounds were estimated. Ultraviolet absorption spectra of the ethers were measured between 160 and 220 nm. The general pattern of reactivity of hydrofluoroethers toward OH is discussed.