Atmospheric chemistry of CF 3 CHFCF 2 OCH 3 (HFE-356mec3) and CHF 2 CHFOCF 3 (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 CF 3 CHFCF 2 OCH 3 (HFE-356mec3) and CHF 2 CHFOCF 3 (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 OH (T) in cm 3 s -1 ) between 263 and 353 K are well described by the following expressions: 9.93 × 10 -13 exp{-(988 ± 35)/T}for HFE-356mec3 and 4.75 × 10 -13 exp{-(1285 ± 22)/T} for HFE-236ea1. Under NO x -free conditions, the rate coefficients k Cl at 298 K and 1013 mbar (760 Torr) of air were determined to be (2.30 ± 1.08) × 10 -13 cm 3 s -1 and (1.19 ± 0.10) × 10 -15 cm 3 s -1 , for HFE-356mec3 and HFE-236ea1, respectively. Additionally, the relative kinetic study of the Cl + CH 2 ClCHCl 2 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 CH 3 CCl 3 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 -2 ppv -1 ) 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.