Atmospheric chemistry of Z- and E-CF3CHCHCF3

Abstract

The atmospheric fates of Z- and E-CF₃CHCHCF₃ have been studied, investigating the kinetics and the products of the reactions of the two compounds with Cl atoms, OH radicals, OD radicals, and O₃. FTIR smog chamber experiments measured: k(Cl + Z-CF₃CHCHCF₃) = (2.59 ± 0.47) × 10⁻¹¹, k(Cl + E-CF₃CHCHCF₃) = (1.36 ± 0.27) × 10⁻¹¹, k(OH + Z-CF₃CHCHCF₃) = (4.21 ± 0.62) × 10⁻¹³, k(OH + E-CF₃CHCHCF₃) = (1.72 ± 0.42) × 10⁻¹³, k(OD + Z-CF₃CHCHCF₃) = (6.94 ± 1.25) × 10⁻¹³, k(OD + E-CF₃CHCHCF₃) = (5.61 ± 0.98) × 10⁻¹³, k(O₃ + Z-CF₃CHCHCF₃) = (6.25 ± 0.70) × 10⁻²², and k(O₃ + E-CF₃CHCHCF₃) = (4.14 ± 0.42) × 10⁻²² cm³ molecule⁻¹ s⁻¹ in 700 Torr of air/N₂/O₂ diluents at 296 ± 2 K. E-CF₃CHCHCF₃ reacts with Cl atoms to give CF₃CHClC(O)CF₃ in a yield indistinguishable from 100%. Z-CF₃CHCHCF₃ reacts with Cl atoms to give (95 ± 10)% CF₃CHClC(O)CF₃ and (7 ± 1)% E-CF₃CHCHCF₃. CF₃CHClC(O)CF₃ reacts with Cl atoms to give the secondary product CF₃C(O)Cl in a yield indistinguishable from 100%, with the observed co-products C(O)F₂ and CF₃O₃CF₃. The main atmospheric fate for Z- and E-CF₃CHCHCF₃ is reaction with OH radicals. The atmospheric lifetimes of Z- and E-CF₃CHCHCF₃ are estimated as 27 and 67 days, respectively. IR absorption cross sections are reported and the global warming potentials (GWPs) of Z- and E-CF₃CHCHCF₃ for the 100 year time horizon are calculated to be GWP₁₀₀ = 2 and 7, respectively. This study provides a comprehensive description of the atmospheric fate and impact of Z- and E-CF₃CHCHCF₃.