Atmospheric chemistry of (Z)- and (E)-1,2-dichloroethene: kinetics and mechanisms of the reactions with Cl atoms, OH radicals, and O3
*ab
Sofie A.
Hass,
b
Theis I.
Sølling,
bc
Timothy J.
Wallington
d
and
Ole J.
Nielsen
b
Abstract
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![[double bond, length as m-dash]](https://www.rsc.org/images/entities/char_e001.gif)
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.
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