OH-initiated degradation of methyl 2-chloroacetoacetate and ethyl 2-chloroacetoacetate: Kinetics, products and mechanisms at 298 K and atmospheric pressure

Abstract

Rate coefficients for the gas-phase reactions of OH radicals with CH3C(O)CHClC(O)OCH3 (k1) and CH3C(O)CHClC(O)OCH2CH3 (k2) were measured using the relative technique with different reference compounds. The experiments were performed at (298 ± 2) K and 750 Torr of nitrogen or synthetic air by in situ FTIR spectroscopy and GC-FID chromatography. The following rate coefficients (in units of cm3molecule−1 s−1) were obtained: k1 FTIR= (2.70 ± 0.51) × 10−11; k1 GC-FID= (2.30 ± 0.71) × 10−11 and k2 FTIR= (3.37 ± 0.62) × 10−11; k2 GC-FID= (3.26 ± 0.85) × 10−11. This work reports the first kinetic study for the reactions of OH radicals with the mentioned chloroacetoacetates. Additionally, product studies are reported in similar conditions of the kinetic experiments. Acetic acid, acetaldehyde, formyl chloride, and methyl 2-chloro-2-oxoacetate were positively identified and quantified as degradation products. According to the identified products, atmospheric chemical mechanisms were proposed. The environmental implications of these reactions were assessed by the tropospheric lifetimes calculations of the title chloroesters. Significant average ozone production of 4.16 ppm for CH3C(O)CHClC(O)OCH3 and 5.98 ppm for CH3C(O)CHClC(O)OCH2CH3, respectively were calculated.