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Photochemical Properties of Some Cl-Containing Halogenated Alkanes

Published

Author(s)

Vladimir L. Orkin, Victor Khamaganov, E. E. Kasimovskaya, A G. Guschin

Abstract

Rate constants for the gas phase reactions of OH radicals with three partially halogenated alkanes, CHCl3 (kMC), CHFClCFCl2 (k122a), and CH2CFCl2 (k132c), were measured using a discharge flow – electron paramagnetic resonance technique over the temperature range 298 K to 460 K. The temperature dependences of the rate constants can be represented by the following expressions: kMC(298-460 K) = (3.9 ± 0.94)×10-12×exp{-(1411 ± 85)/T)} cm3 molecule-1 s-1; k122a(298-460 K) = (1.26 ± 0.24)×10-12×exp{-(1298 ± 66)/T)} cm3 molecule-1 s-1; k132c(298-370 K) = (8.1 ± 2.2)×10-13×exp{-(1247 ± 89)/T)} cm3 molecule-1 s-1. Based on the analysis of the available data, the following expression is recommended for kMC(T) at below room temperatures of atmospheric interest: kMC(220-298 K) = 1.95×10-12×exp{-1200/T} cm3 molecule-1 s-1. The atmospheric lifetimes of CHCl3, CHFClCFCl2, and CH2CFCl2 due to their reaction with OH were estimated to be 1.6, 3.5, and 4.5 years, respectively. The UV absorption cross-sections of these compounds were measured at T = 295 K between 190 nm and 240 nm as well as those for CHCl2CF2Cl (HCFC-122), CHCl2CF3 (HCFC-123), CHFClCF2Cl (HCFC-123a), and CH3CFCl2 (HCFC-141b).
Citation
Atmospheric Environment

Keywords

hydroxyl, atmospheric lifetime, methyl chloride, HCFC-122a, HCFC-132c, 1, 1, 2-trichloro-1, 2-difluoroethane, 1, 1-dichloro-1, 2-difluoroethane
Created May 31, 2013, Updated March 16, 2017