An Investigation of the Reactivity of OH with Fluoroethanes:  CH3CH2F (HFC-161), CH2FCH2F (HFC-152), and CH3CHF2 (HFC-152a)

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2003-04, Vol.107 (13), p.2239-2246
• Main Authors: Kozlov, Sergey N, Orkin, Vladimir L, Kurylo, Michael J
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp022087b

Rate constants for the reactions of OH radicals with fluoroethane (CH3CH2F), 1,2-difluoroethane (CH2FCH2F), and 1,1-difluoroethane (CH3CHF2) were measured using the flash photolysis resonance−fluorescence technique over the temperature range of T = 210−480 K. Arrhenius plots for all three reactions exhibit noticeable curvature, and the rate constants are well represented by three-parameter modified Arrhenius expressions over the full experimental temperature range, with better than 3% precision:  k CH 3 CH 2 F(T) = 3.14 × 10-13(T/298)2.45 exp{−103/T} cm3 molecule-1 s-1, k CH 2 FCH 2 F(T) = 4.33 × 10-14(T/298)3.85 exp{+247/T} cm3 molecule-1 s-1, and k CH 3 CHF 2 (T) = 7.72 × 10-14(T/298)3.02 exp{−247/T} cm3 molecule-1 s-1. For the temperature range of atmospheric interest (T < 300 K), the rate constants can be well represented by standard (two-parameter) Arrhenius expressions. On the basis of all the available low-temperature data, the following rate constants are recommended for atmospheric modeling:  k CH 3 CH 2 F(T < 300 K) = 2.55 × 10-12 exp{−730/T} cm3 molecule-1 s-1, k CH 2 FCH 2 F(T < 300 K) = 1.12 × 10-12 exp{−730/T} cm3 molecule-1 s-1, and k CH 3 CHF 2 (T < 300 K) = 0.94 × 10-12 exp{−990/T} cm3 molecule-1 s-1. Using these recommendations, atmospheric lifetimes were estimated to be ca. 2.4 months, 5.5 months, and 1.4 years for CH3CH2F, CH2FCH2F, and CH3CHF2, respectively.