Journal of Physical Chemistry A, Vol.118, No.46, 11015-11025, 2014
OH plus (E)- and (Z)-1-Chloro-3,3,3-trifluoropropene-1 (CF3CH equivalent to CHCI) Reaction Rate Coefficients: Stereoisomer-Dependent Reactivity
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) (k(1)(T) and k(2)(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, N-2) with k(1)(296 K) = (3.76 +/- 0.35) x 10(-13) cm(3) molecule(-1) s(-1) and k(2)(296 K) = (9.46 +/- 0.85) x 10(-13) cm(3) molecule(-1) s(-1) (quoted uncertainties are 2s 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 k(1)(T) = (1.14 +/- 0.15) x 10(-12) exp[(-330 +/- 10)/T] cm(3) molecule(-1) s(-1) and k(2)(T) = (7.22 +/- 0.65) x 10(-19) x T-2 x 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 O-2. 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 similar to 34 and similar to 11 days, respectively. Infrared absorption spectra measured in this work were used to estimate radiative efficiencies and well-mixed global warming potentials of similar to 10 and similar to 3 for (E)- and (Z)-CF3CH-CHCl, respectively, on the 100-year time horizon.