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

Smog chambers interfaced with in situ FT-IR detection were used to investigate the kinetics and mechanisms of the Cl atom, OH radical, and O₃ initiated oxidation of (Z)- and (E)-1,2-dichloroethene (CHCl 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 CHCl) under atmospheric conditions. Relative and absolute rate methods were used to measure k(Cl + (Z)-CHClCHCl) = (8.80 ± 1.75) × 10⁻¹¹, k(Cl + (E)-CHClCHCl) = (8.51 ± 1.69) × 10⁻¹¹, k(OH + (Z)-CHClCHCl) = (2.02 ± 0.43) × 10⁻¹², k(OH + (E)-CHClCHCl) = (1.94 ± 0.43) × 10⁻¹², k(O₃ + (Z)-CHClCHCl) = (4.50 ± 0.45) × 10⁻²¹, and k(O₃ + (E)-CHClCHCl) = (1.02 ± 0.10) × 10⁻¹⁹ cm³ molecule⁻¹ s⁻¹ in 700 Torr of N₂/air diluent at 298 ± 2 K. Pressure dependencies for the Cl atom reaction kinetics were observed for both isomers, consistent with isomerization occurring via Cl atom elimination from the chemically activated CHCl-CHCl-Cl adduct. The observed products from Cl initiated oxidation were HC(O)Cl (117-133%), CHCl₂CHO (29-30%), and the corresponding CHClCHCl isomer (11-20%). OH radical initiated oxidation gives HC(O)Cl as a major product. For reaction of OH with (E)-CHClCHCl, (Z)-CHClCHCl was also observed as a product. A significant chlorine atom elimination channel was observed experimentally (HCl yield) and supported by computational results. Photochemical ozone creation potentials of 12 and 11 were estimated for (Z)- and (E)-CHClCHCl, respectively. Finally, an empirical kinetic relationship is explored for the addition of OH radicals or Cl atoms to small alkenes. The results are discussed in the context of the atmospheric chemistry of (Z)- and (E)-CHClCHCl.