OH + (E)- And (Z)-1-chloro-3,3,3-trifluoropropene-1 (CF3CH═CHCl) Reaction Rate Coefficients: Stereoisomer-Dependent Reactivity

Tomasz Gierczak, M Baasandorj, James B Burkholder

J Phys Chem A. 2014 Nov 20;118(46):11015-25.

PMID: 25333607

Abstract:

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) cm(3) molecule(-1) s(-1) and k2(296 K) = (9.46 ± 0.85) × 10(-13) cm(3) 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] cm(3) molecule(-1) s(-1) and k2(T) = (7.22 ± 0.65) × 10(-19) × T(2) × exp[(800 ± 20)/T] cm(3) 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.