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

Abstract

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·F2OCF2CHFCl and CHF2OCF2C·FCl are observed, and the formation of CHF2OCF2C·FCl is found to be more favorable than C·F2OCF2CHFCl kinetically and thermodynamically. Subsequent evolution of CHF2OCF2C·FCl in the presence of NO and O2 indicates that the organic nitrate (CHF2OCF2CONO2FCl) is the stable product. The dechlorinate of alkoxy radical (CHF2OCF2C(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 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.

Hydroxyl‐initiated oxidation processes of phenylenediamines treated by the atmospheric plasma: A theoretical study in gas phase

“…In atmospheric chemistry, OH‐initiated oxidation processes have been well studied. Yang et al used M062X/6‐311G(d,p) methods to find the optimized geometries of transition states for CTDE and used CCSD(T), QCISD(T) methods to calculate single point energies [26]. The calculations of Dwinandha et al shows that M062X has the highest accuracy compared with HF and B3LYP using basis sets 6‐311+G(2d,2p) [25].…”