Atmospheric oxidation of selected chlorinated alkenes by O₃, OH, NO₃ and Cl

An experimental study on the 3-chloro-2-methyl-1-propene (CMP), 2,3-dichloropropene (DCP) and 3,4-dichlorobutene (DCB) reactions with atmospheric oxidants at (298 ± 1) K and atmospheric pressure is reported. Rate constants for the gas phase reactions of the three chlorinated alkenes with O₃, OH and NO₃ radicals and Cl atom were determined in a 100 L Teflon reactor by gas chromatography with flame ionization detector (GC-FID). The obtained rate constants are (3.03 ± 0.15) × 10⁻¹⁸, (3.83 ± 1.30) × 10⁻¹¹, (1.99 ± 0.19) × 10⁻¹⁴, and (2.40 ± 0.41) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ for CMP reactions with O₃, OH, NO₃, and Cl, respectively, (4.62 ± 1.41) × 10⁻²⁰, (1.37 ± 1.02) × 10⁻¹¹, (1.45 ± 0.15) × 10⁻¹⁵ and (1.30 ± 0.99) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ for DCP reactions and (2.09 ± 0.24) × 10⁻¹⁹, (1.45 ± 0.59) × 10⁻¹¹, (3.00 ± 0.82) × 10⁻¹⁶ and (1.91 ± 0.19) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ for DCB reactions. The CMP reaction products were detected and possible reaction mechanisms of their formation were proposed. Chloroacetone was found to be the major product in all four oxidation reactions. The loss process of CMP in the atmosphere is mostly controlled by its reaction with the OH radical during daytime and with NO₃ during nighttime, with lifetimes of 3.6 h and 27.9 h respectively. Atmospheric implications of both these reactions and their potential products are discussed.