Atmospheric chemistry of (E)-1,2-difluoroethene: kinetics and mechanisms of the reactions with Cl atoms, OH radicals and O3

Abstract

Smog chamber experiments were used to investigate the kinetics and mechanisms of the Cl atom, OH radical and O₃ initiated oxidation of (E)-1,2-difluoroethene (CHFCHF) at (298 ± 2) K under atmospheric conditions. Relative and absolute rate methods were used to measure k(Cl + (E)-CHFCHF) = (1.00 ± 0.12) × 10⁻¹⁰, k(OH + (E)-CHFCHF) = (8.42 ± 1.29) × 10⁻¹², and k(O₃ + (E)-CHFCHF) = (1.16 ± 0.07) × 10⁻¹⁸ cm³ molecule⁻¹ s⁻¹ in 700 Torr of N₂/air diluent. A slight pressure dependence for the kinetics of the Cl initiated oxidation was observed: 13% reduction at 50 Torr compared to atmospheric pressure. The observed products from the reaction of (E)-CHFCHF with Cl were HC(O)F and the corresponding (Z)-CHFCHF isomer (14% at 700 Torr, 62% at 50 Torr total pressure). In the OH radical initiated oxidation, the major product observed was HC(O)F in a yield of (205 ± 8)%. The O₃ initiated oxidation leads to HC(O)F and HF in yields of (148 ± 4)% and (53 ± 2)%, respectively. As part of this study the chlorine kinetics of the Z-isomer of the title compound was determined as k(Cl + (Z)-CHFCHF) = (1.21 ± 0.25) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. The photochemical ozone creation potential, the radiative efficiency, and global warming potentials are estimated, and the results are discussed in the context of the atmospheric chemistry of (E)-CHFCHF and other halogenated alkenes.