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

The transformation mechanism and kinetics of 2-chloro-1,1,2-trifluoroethyl- difluoromethyl-ether (CTDE, CHF 2 OCF 2 CHFCl) 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?F 2 OCF 2 CHFCl and CHF 2 OCF 2 C?FCl are observed, and the formation of CHF 2 OCF 2 C?FCl is found to be more favorable than C?F 2 OCF 2 CHFCl kinetically and thermodynamically. Subsequent evolution of CHF 2 OCF 2 C?FCl in the presence of NO and O 2 indicates that the organic nitrate (CHF 2 OCF 2 CONO 2 FCl) is the stable product. The dechlorinate of alkoxy radical (CHF 2 OCF 2 C(O?)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 contribu- tions 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.