Atmospheric chemistry of CFCHFCFOCH (HFE-356mec3) and CHFCHFOCF (HFE-236ea1) initiated by OH and Cl and their contribution to global warming.

The kinetic study of the gas-phase reactions of hydroxyl (OH) radicals and chlorine (Cl) atoms with CFCHFCFOCH (HFE-356mec3) and CHFCHFOCF (HFE-236ea1) was performed by the pulsed laser photolysis/laser-induced fluorescence technique and a relative method by using Fourier Transform infrared (FTIR) spectroscopy as detection technique. The temperature dependences of the OH-rate coefficients (k(T) in cms) between 263 and 353 K are well described by the following expressions: 9.93 × 10exp{-(988 ± 35)/T}for HFE-356mec3 and 4.75 × 10exp{-(1285 ± 22)/T} for HFE-236ea1. Under NO-free conditions, the rate coefficients k at 298 K and 1013 mbar (760 Torr) of air were determined to be (2.30 ± 1.08) × 10 cmsand (1.19 ± 0.10) × 10 cms, for HFE-356mec3 and HFE-236ea1, respectively. Additionally, the relative kinetic study of the Cl + CHClCHCl reaction was investigated at 298 K, as it was used as a reference reaction in the kinetic study of the Cl-reaction with HFE-356mec3 and discrepant rate coefficients were found in the literature. The global atmospheric lifetimes were estimated relative to CHCCl at the tropospheric mean temperature (272 K) as 1.4 and 8.6 years for HFE-356mec3 and HFE-236ea1, respectively. These values combined with the radiative efficiencies for HFE-356mec3 and HFE-236ea1 derived from the measured IR absorption cross sections (0.27 and 0.41 W m ppv) yield global warming potentials at a 100-yrs time horizon of 143 and 1473, respectively. The contribution of HFE-356mec3 and HFE-236ea1 to global warming of the atmosphere would be large if they become widespread increasing their atmospheric concentration.