Relative Rate and Product Studies of the Reactions of Atomic Chlorine with Tetrafluoroethylene, 1,2-Dichloro-1,2-difluoroethylene, 1,1-Dichloro-2,2-difluoroethylene, and Hexafluoro-1,3-butadiene in the Presence of Oxygen

Rate coefficients k₁–k₃ have been measured for Cl atom reactions with CF₂CF₂, CFClCFCl, and CCl₂CF₂ relative to k₄ for CF₂CF–CFCF₂ at 293 ± 2 K. k₄ was remeasured relative to Cl + ethane. Cl was generated by UV photolysis of Cl₂, and other species were monitored by FT-IR spectroscopy. The measurements yield k₁ = (6.6 ± 1.0) × 10^–11, k₂ = (6.5 ± 1.0) × 10^–11, and k₃ = (7.1 ± 1.1) × 10^–11 cm³ molecule^–1 s^–1, respectively, and k₄ = (8.0 ± 1.2) × 10^–11 cm³ molecule^–1 s^–1 is proposed. These results are discussed in the context of atmospheric chemistry. Subsequent chemistry in the presence of oxygen leads to oxygenated products that are identified via their IR spectra, and possible mechanisms are discussed. The yield of CF₂O from C₂F₄ is 93 ± 7%. Dichlorofluoroacetyl fluoride (CCl₂FCFO) was observed as a product from CFClCFCl, and chlorodifluoroacetyl chloride (CClF₂CClO) was observed from CCl₂CF₂ oxidation. C₄F₆ led to 66 ± 5% CF₂O and 38 ± 3% OCF₂CFC­(F)O. Reaction enthalpies and enthalpy barriers computed via CBS-QB3 theory help rule out some unfavorable mechanistic steps.