Theoretical insight into OH- and Cl-initiated oxidation of CF₃OCH(CF₃)₂ and CF₃OCF₂CF₂H &fate of CF₃OC(X•)(CF₃)₂ and CF₃OCF₂CF₂X• radicals (X=O, O₂).

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: k _T(1)?=?5.00?×?10^-24T^3.57 exp(-849.73/T), k _T(2)?=?1.79?×?10^-24T^4.84 exp(-4262.65/T), k_T(3)?=?1.94?×?10^-24 T^4.18 exp(-884.26/T), and k _T(4)?=?9.44?×?10^-28T^5.25 exp(-913.45/T) cm³ molecule^-1 s^-1.

SUBMITTER: Bai FY 

PROVIDER: S-EPMC5220334 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature