A study of the self reaction of CH2ClO2 and CHCl2O2 radicals at 298 K

A low-pressure discharge-flow system equipped with laser-induced fluorescence (LIF) detection of NO2 and resonance-fluorescence detection of OH has been employed to study the self reactions CH2ClO2 + CH2ClO2 products (1) and CHCl2O2 + CHCl2O2 products (2), at T = 298 K and P = 1–3 Torr. Possible secondary reactions involving alkoxy radicals are identified. We report the phenomenological rate constants (kobs) k1obs = (4.1 ± 0.2) × 10−12 cm3 molecule−1 s−1k2obs = (8.6 ± 0.2) × 10−12 cm3 molecule−1 s−1 and the rate constants derived from modelling the decay profiles for both peroxy radical systems, which takes into account the proposed secondary chemistry involving alkoxy radicals k1 = (3.3 ± 0.7) × 10−12 cm3 molecule−1 s−1k2 = (7.0 ± 1.8) × 10−12 cm3 molecule−1 s−1 A possible mechanism for these self reactions is proposed and QRRK calculations are performed for reactions (1), (2) and the self-reaction of CH3O2, CH3O2 + CH3O2 products (3). These calculations, although only semiquantitative, go some way to explaining why both k1 and k2 are a factor of ten larger than k3 and why, as suggested by the products of reaction (1) and (2), it seems that the favored reaction pathway is different from that followed by reaction (3). The atmospheric fate of the chlorinated peroxy species, and hence the impact of their precursors (CH3Cl and CH2Cl2), in the troposphere are briefly discussed. HC(O)Cl is identified as a potentially important reservoir species produced from the photooxidation of these precursors. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 433–444, 1999