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Rate Coefficients for the Gas-Phase Reaction of (E)- and (Z)‑CF3CFHCFCF3 with...

Baasandorj, M., V. C. Papadimitriou, and J. Burkholder (2019), Rate Coefficients for the Gas-Phase Reaction of (E)- and (Z)‑CF3CFHCFCF3 with the OH Radical and Cl-Atom, J. Phys. Chem. A, 123, 5051-5060, doi:10.1021/acs.jpca.9b03095.

The rate coefficients, k, for the gas-phase reaction of the OH radical and Cl-atom with (E)- and (Z)CF3CFHCFCF3 were measured using a relative rate technique over a range of temperature (240−375 K) and bath gas pressure (50−630 Torr, He). The obtained rate coefficients were found to be independent of pressure under these conditions. The obtained rate coefficients for the reaction of Cl-atom with (E)- and (Z)-CF3CFHCFCF3 at 296 K were k1(296 K) = (7.23 ± 0.3) × 10−12 cm3 molecule−1 s−1 and k2(296 K) = (6.70 ± 0.3) × 10−12 cm3 molecule−1 s−1, respectively, with the temperature dependence described by the Arrhenius expressions: k1(T) = (3.47 ± 0.35) × 10−12 exp[(210 ± 25)/T] cm3 molecule−1 s−1 and k2(T) = (3.37 ± 0.35) × 10−12 exp[(199 ± 25)/T] cm3 molecule−1 s−1. The rate coefficients for the OH radical reaction with (E)- and (Z)CF3CFHCFCF3 were found to be k3(296−375 K) = (4.34 ± 0.45) × 10−13 cm3 molecule−1 s−1 and k4(296−375 K) = (3.30 ± 0.35) × 10−13 cm3 molecule−1 s−1, respectively. The quoted rate coefficient uncertainties are 2σ (95% confidence level) and include estimated systematic errors. The rate coefficients for the reaction of OH with a mixture of the two stereoisomers were determined using a pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) technique for comparison with previous kinetic measurements using stereoisomer mixtures. The effective rate coefficient for the 0.7/0.3 (E)/(Z) stereoisomer sample was found to be nearly independent of temperature over the range 222−375 K with a value of (4.47 ± 0.36) × 10−13 cm3 molecule−1 s−1. The atmospheric lifetimes for (E)- and (Z)-CF3CFHCFCF3 due to OH-reactive loss are estimated to be 25 and 35 days, respectively. The lifetime-corrected radiative efficiencies (W m−2 ppb−1) and 100 year time horizon global warming potentials derived in this work are 0.05 and 1.2 for (E)-CF3CFHCFCF3 and 0.13 and 4.1 for (Z)-CF3CFHCFCF3. The photochemical ozone creation potentials for (E)- and (Z)-CF3CFHCFCF3 are estimated to be 2.5 and 2.1, respectively.

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Atmospheric Composition