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

Abstract

Rate coefficients for the gas-phase reaction of the OH radical with (<i>E</i>)- and (<i>Z</i>)-CF₃CHCHCl (1-chloro-3,3,3-trifluoropropene-1, HFO-1233zd) (<i>k</i>₁(<i>T</i>) and <i>k</i>₂(<i>T</i>), 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 <i>k</i>₁(296 K) = (3.76 ± 0.35) × 10^–13 cm³ molecule^–1 s^–1 and <i>k</i>₂(296 K) = (9.46 ± 0.85) × 10^–13 cm³ molecule^–1 s^–1 (quoted uncertainties are 2σ and include estimated systematic errors). <i>k</i>₂(<i>T</i>) showed a weak non-Arrhenius behavior over this temperature range. The (<i>E</i>)- and (<i>Z</i>)- stereoisomer rate coefficients were found to have opposite temperature dependencies that are well represented by <i>k</i>₁(<i>T</i>) = (1.14 ± 0.15) × 10^–12 exp[(−330 ± 10)/<i>T</i>] cm³ molecule^–1 s^–1 and <i>k</i>₂(<i>T</i>) = (7.22 ± 0.65) × 10^–19 × <i>T</i>² × exp[(800 ± 20)/<i>T</i>] cm³ molecule^–1 s^–1. The present results are compared with a previous room temperature relative rate coefficient study of <i>k</i>₁, 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 (<i>E</i>)- and (<i>Z</i>)-CF₃CHCHCl in the presence of O₂. In addition, chemically activated isomerization was also observed. Atmospheric local lifetimes of (<i>E</i>)- and (<i>Z</i>)-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 (<i>E</i>)- and (<i>Z</i>)-CF₃CHCHCl, respectively, on the 100-year time horizon