Atmospheric chemistry of ( Z )- and ( E )-1,2-dichloroethene: kinetics and mechanisms of the reactions with Cl atoms, OH radicals, and O 3 .

Smog chambers interfaced with in situ FT-IR detection were used to investigate the kinetics and mechanisms of the Cl atom, OH radical, and O 3 initiated oxidation of ( Z )- and ( E )-1,2-dichloroethene (CHClCHCl) under atmospheric conditions. Relative and absolute rate methods were used to measure k (Cl + ( Z )-CHClCHCl) = (8.80 ± 1.75) × 10 -11 , k (Cl + ( E )-CHClCHCl) = (8.51 ± 1.69) × 10 -11 , k (OH + ( Z )-CHClCHCl) = (2.02 ± 0.43) × 10 -12 , k (OH + ( E )-CHClCHCl) = (1.94 ± 0.43) × 10 -12 , k (O 3 + ( Z )-CHClCHCl) = (4.50 ± 0.45) × 10 -21 , and k (O 3 + ( E )-CHClCHCl) = (1.02 ± 0.10) × 10 -19 cm 3 molecule -1 s -1 in 700 Torr of N 2 /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%), CHCl 2 CHO (29-30%), and the corresponding CHClCHCl isomer (11-20%). OH radical initiated oxidation gives HC(O)Cl as a major product. For reaction of OH with ( E )-CHClCHCl, ( Z )-CHClCHCl 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 )-CHClCHCl, 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 )-CHClCHCl.