title: Theoretical and kinetic studies of the reactions of CF(2)HCFHCF(2)H and CF(3)CFHCFH(2) with hydroxyl radicals.
abstract: The hydrogen abstraction reactions of fluoroalkane isomers CF(2)HCFHCF(2)H and CF(3)CFHCFH(2) with the OH radicals have been studied theoretically by a dual-level direct dynamics method. Optimized geometries and frequencies of all the stationary points and extra points along the minimum-energy path are obtained at the BB1K/6-31+G(d,p) level of theory, and then the energy profiles are refined at G3(MP2) level of theory. Using the improved canonical variational transition-state theory (ICVT) with the small-curvature tunneling correction (SCT), the rate constants for each channel are calculated over a wide temperature range of 200-1000 K. Our results show that the tunneling correction plays an important role in the rate constant calculation in the low temperature range. The calculated ICVT/SCT rate constants are consistent with available experimental data. Our calculations indicate the contribution of the abstraction from the -CFH- group of isomeric compounds CF(2)HCFHCF(2)H and CF(3)CFHCFH(2) to the overall reactions is quite different over the whole temperature range due to the effect of different groups at both sides of -CFH- group. Furthermore, to further reveal the thermodynamic properties, the enthalpies of formation of the two reactants CF(2)HCFHCF(2)H, and CF(3)CFHCFH(2), and the product radicals CF(2)HCFCF(2)H, CF(2)HCFHCF(2), CF(3)CFCFH(2), and CF(3)CFHCFH are obtained by using isodesmic reactions.
authors.affiliation: Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, People's Republic of China.
authors.forename: Hong
authors.initials: H
authors.lastname: Gao
authors.forename: Jing-yao
authors.initials: JY
authors.lastname: Liu
authors.forename: Chia-chung
authors.initials: CC
authors.lastname: Sun
mesh_terms: D003198:Computer Simulation; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical
chemical_list: D006845:Hydrocarbons, Fluorinated; D017665:Hydroxyl Radical