Atmospheric chemistry of CHF_2CF_2OCH_2CF_3: Reactions with CI atoms, fate of CHF_2CF_2O•HCF_3 radical, formation of OH radical and Criegee Intermediate

摘要

The kinetics and mechanism for hydrogen abstraction reactions of CHF2CF2OCH2CF3 with Cl atoms were studied using the DFT-based M06-2X/6-311++G(d,p) quantum chemical method. The thermal rate coefficients for Habstraction reactions were evaluated by canonical variational transition state theory along with the small curvature tunneling correction over the temperature range of 200-1000 K. A three-parameter model equation has been proposed to describe the temperature variation of rate coefficient as k(CHF2CF2OCH2CF3+Cl) = 5.24 x 10(-22) T(3.2)exp(-580/T)(in cm(3) molecule(-1) s(-1)). Atmospheric lifetime of CHF2CF2OCH2CF3 is estimated to be 3.10 years and global warming potentials at the 100-year time horizon is calculated as 601. The atmospheric fate of generated CHF2CF2OC center dot HCF3 radical are reported. The rate coefficient values for the reaction of important degradation products like CHF2CF2OCHO and CHF2CF2OOH with OH/Cl are also reported for the first time. Production of OH radicals from the unimolecular decomposition of CHF2CF2OC(OO center dot)HCF3 pemxy radical and the possible formation of Fluorinated Criegee Intermediate from self-reaction of RO2 radicals are discussed.