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Download file# Rate Coefficient Measurements and Theoretical Analysis
of the OH + (*E*)‑CF_{3}CHCHCF_{3} Reaction

journal contribution

posted on 2018-04-25, 00:00 authored by Munkhbayar Baasandorj, Paul Marshall, Robert L. Waterland, A.R. Ravishankara, James B. BurkholderRate
coefficients,

*k*, for the gas-phase reaction of the OH radical with (*E*)-CF_{3}CHCHCF_{3}((*E*)-1,1,1,4,4,4-hexafluoro-2-butene, HFO-1336mzz(E)) were measured over a range of temperatures (211–374 K) and bath gas pressures (20–300 Torr; He, N_{2}) using a pulsed laser photolysis–laser-induced fluorescence (PLP–LIF) technique.*k*_{1}(*T*) was independent of pressure over this range of conditions with*k*_{1}(296 K) = (1.31 ± 0.15) × 10^{–13}cm^{3}molecule^{–1}s^{–1}and*k*_{1}(*T*) = (6.94 ± 0.80) × 10^{–13}exp[−(496 ± 10)/*T*] cm^{3}molecule^{–1}s^{–1}, where the uncertainties are 2σ, and the pre-exponential term includes estimated systematic error. Rate coefficients for the OD reaction were also determined over a range of temperatures (262–374 K) at 100 Torr (He). The OD rate coefficients were ∼15% greater than the OH values and showed similar temperature dependent behavior with*k*_{2}(*T*) = (7.52 ± 0.44) × 10^{–13}exp[−(476 ± 20)/*T*] and*k*_{2}(296 K) = (1.53 ± 0.15) × 10^{–13}cm^{3}molecule^{–1}s^{–1}. The rate coefficients for reaction 1 were also measured using a relative rate technique between 296 and 375 K with*k*_{1}(296 K) measured to be (1.22 ± 0.1) × 10^{–13}cm^{3}molecule^{–1}s^{–1}, in agreement with the PLP–LIF results. In addition, the 296 K rate coefficient for the O_{3}+ (*E*)-CF_{3}CHCHCF_{3}reaction was determined to be <5.2 × 10^{–22}cm^{3}molecule^{–1}s^{–1}. A theoretical computational analysis is presented to interpret the observed positive temperature dependence for the addition reaction and the significant decrease in OH reactivity compared to the (*Z*)-CF_{3}CHCHCF_{3}stereoisomer reaction. The estimated atmospheric lifetime of (*E*)-CF_{3}CHCHCF_{3}, due to loss by reaction with OH, is estimated to be ∼90 days, while the actual lifetime will depend on the location and season of its emission. Infrared absorption spectra of (*E*)-CF_{3}CHCHCF_{3}were measured and used to estimate the 100 year time horizon global warming potentials (GWP) of 32 (atmospherically well-mixed) and 14 (lifetime-adjusted).