Abstract
In this study, the mechanistic and kinetic analysis for reactions of CF3OCH(CF3)2 and CF3OCF2CF2H with OH radicals and Cl atoms have been performed at the CCSD(T)//B3LYP/6-311++G(d,p) level. Kinetic isotope effects for reactions CF3OCH(CF3)2/CF3OCD(CF3)2 and CF3OCF2CF2H/CF3OCF2CF2D with OH and Cl were estimated so as to provide the theoretical estimation for future laboratory investigation. All rate constants, computed by canonical variational transition state theory (CVT) with the small-curvature tunneling correction (SCT), are in reasonable agreement with the limited experimental data. Standard enthalpies of formation for the species were also calculated. Atmospheric lifetime and global warming potentials (GWPs) of the reaction species were estimated, the large lifetimes and GWPs show that the environmental impact of them cannot be ignored. The organic nitrates can be produced by the further oxidation of CF3OC(•)(CF3)2 and CF3OCF2CF2• in the presence of O2 and NO. The subsequent decomposition pathways of CF3OC(O•)(CF3)2 and CF3OCF2CF2O• radicals were studied in detail. The derived Arrhenius expressions for the rate coefficients over 230–350 K are: kT(1) = 5.00 × 10−24T3.57 exp(−849.73/T), kT(2) = 1.79 × 10−24T4.84 exp(−4262.65/T), kT(3) = 1.94 × 10−24T4.18 exp(−884.26/T), and kT(4) = 9.44 × 10−28T5.25 exp(−913.45/T) cm3 molecule−1 s−1.
Highlights
During these years, many theoretical[9,10,11,12,13,14,15,16,17] and experimental[18,19,20,21,22,23] investigations about the reactions of some volatile organic compounds (VOCs) with free radicals have been carried out in kinetic properties, reaction mechanisms, temperature dependence and more
As for the prototypical species of HFEs, CF3OCH(CF3)[2] and CF3OCF2CF2H can be attacked by OH radicals and Cl atoms by the following reaction channels: CF3OCH(CF3)2 + OH T→S1 CF3OC(CF3)2 + H2O
At the B3LYP/6-311++G(d,p) and M06-2X/6-311++G(d,p) levels, the optimized structural parameters of the reactants, products, complexes, and transition states for reactions of CF3OCH(CF3)2 +OH/Cl and CF3OCF2CF2H (a, b) +OH/Cl are shown in Figure S1, along with the limited experimental bond distance and angle values[29]
Summary
Many theoretical[9,10,11,12,13,14,15,16,17] and experimental[18,19,20,21,22,23] investigations about the reactions of some volatile organic compounds (VOCs) with free radicals have been carried out in kinetic properties, reaction mechanisms, temperature dependence and more. HFEs. In this work, we have carried out a kinetic study of the CF3OCH(CF3)[2] and CF3OCF2CF2H with OH radicals and Cl atoms, using density functional theory (DFT) and the dual-level direct dynamic method. In the present work, high-level ab initio calculations and the dual-level direct dynamics method are performed on the mechanisms and kinetics of CF3OCH(CF3)2 +OH/Cl reactions and the dynamic properties of CF3OCF2CF2H +OH/Cl reactions. Our aim is to gain a further insight into the mechanism of the subsequent behaviors for CF3OC(O)(CF3)[2] and CF3OCF2CF2O radicals This is the first study to reveal the decomposition mechanisms of CF3OC(O)(CF3)[2] and CF3OCF2CF2Oin theory
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