Mechanism, kinetics, and environmental assessment of OH-initiated transformation of CTDE in the atmosphere

The transformation mechanism and kinetics of 2-chloro-1,1,2-trifluoroethyl-difluoromethyl-ether (CTDE, CHF2OCF2CHFCl) triggered by OH radicals are studied by density-functional theory methods and canonical variational transition state theory. The computational rate constant including small-curvature tunneling correction is found to be in commendable agreement with the experimental data. Two hydrogen abstraction channels to form the alkyl radicals of C center dot F2OCF2CHFCl and CHF2OCF2C center dot FCl are observed, and the formation of CHF2OCF2C center dot FCl is found to be more favorable than C center dot F2OCF2CHFCl kinetically and thermodynamically. Subsequent evolution of CHF2OCF2C center dot FCl in the presence of NO and O-2 indicates that the organic nitrate (CHF2OCF2CONO2FCl) is the stable product. The dechlorinate of alkoxy radical (CHF2OCF2C(O center dot)FCl) is the most favorable degradation channel, and the estimated ozone depletion potential for CTDE relative to chlorofluorocarbon-11 is 0.0204, which could lead to ozone depletion as a consequence. The computed atmospheric lifetime for CTDE is found to be 3.69 years by considering the combined contributions from OH radicals and Cl atoms. The total radiative forcing and global warming potential of CTDE are, respectively, 0.547 W m(-2) ppbv and 628.58 (100 years) at 298 K, suggesting that the contribution of CTDE to the greenhouse effect is moderate.