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OH + (E)- and (Z)‑1-Chloro-3,3,3-trifluoropropene‑1 (CF3CHCHCl) Reaction Rate Coefficients: Stereoisomer-Dependent Reactivity

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journal contribution
posted on 20.11.2014, 00:00 authored by Tomasz Gierczak, M. Baasandorj, James B. Burkholder
Rate coefficients for the gas-phase reaction of the OH radical with (E)- and (Z)-CF3CHCHCl (1-chloro-3,3,3-trifluoropropene-1, HFO-1233zd) (k1(T) and k2(T), respectively) were measured under pseudo-first-order conditions in OH over the temperature range 213–376 K. OH was produced by pulsed laser photolysis, and its temporal profile was measured using laser-induced fluorescence. The obtained rate coefficients were independent of pressure between 25 and 100 Torr (He, N2) with k1(296 K) = (3.76 ± 0.35) × 10–13 cm3 molecule–1 s–1 and k2(296 K) = (9.46 ± 0.85) × 10–13 cm3 molecule–1 s–1 (quoted uncertainties are 2σ and include estimated systematic errors). k2(T) showed a weak non-Arrhenius behavior over this temperature range. The (E)- and (Z)- stereoisomer rate coefficients were found to have opposite temperature dependencies that are well represented by k1(T) = (1.14 ± 0.15) × 10–12 exp[(−330 ± 10)/T] cm3 molecule–1 s–1 and k2(T) = (7.22 ± 0.65) × 10–19 × T2 × exp[(800 ± 20)/T] cm3 molecule–1 s–1. The present results are compared with a previous room temperature relative rate coefficient study of k1, and an explanation for the discrepancy is presented. CF3CHO, HC­(O)­Cl, and CF3CClO, were observed as stable end-products following the OH radical initiated degradation of (E)- and (Z)-CF3CHCHCl in the presence of O2. In addition, chemically activated isomerization was also observed. Atmospheric local lifetimes of (E)- and (Z)-CF3CHCHCl, due to OH reactive loss, were estimated to be ∼34 and ∼11 days, respectively. Infrared absorption spectra measured in this work were used to estimate radiative efficiencies and well-mixed global warming potentials of ∼10 and ∼3 for (E)- and (Z)-CF3CHCHCl, respectively, on the 100-year time horizon.