Rate Coefficients For The Gas-Phase Reaction Of (E)- And (Z)-Cf3cf=Cfcf3 With The Oh Radical And Cl-Atom

The rate coefficients, k, for the gas-phase reaction of the OH radical and Cl-atom with (E)- and (Z)-CF3CF=CFCF3 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)-CF3CF=CFCF3 at 296 K were k(1)(296 K) = (7.23 +/- 0.3) x 10(-12) cm(3) molecule(-1) s(-1) and k(2)(296 K) = (6.70 +/- 0.3) x 10(-12) cm(3) molecule(-1) s(-1), respectively, with the temperature dependence described by the Arrhenius expressions: k(1)(T) = (3.47 +/- 0.35) x 10(-12) exp[(210 +/- 25)/T] cm(3) molecule(-1) s(-1) and k(2)(T) = (3.37 +/- 0.35) x 10(-12) exp[(199 +/- 25)/T] cm(3) molecule(-1) s(-1). The rate coefficients for the OH radical reaction with (E)- and (Z)-CF3CF=CFCF3 were found to be k(3)(296-375 K) = (4.34 +/- 0.45) x 10(-13) cm(3) molecule(-1) s(-1) and k(4)(296-375 K) = (3.30 +/- 0.35) x 10(-13) cm(3) molecule(-1) s(-1), respectively. The quoted rate coefficient uncertainties are 2 sigma (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) x 10(-13) cm(3) molecule(-1) s(-1). The atmospheric lifetimes for (E)- and (Z)-CF3CF=CFCF3 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)-CF3CF=CFCF3 and 0.13 and 4.1 for (Z)-CF3CF=CFCF3. The photochemical ozone creation potentials for (E)- and (Z)-CF3CF=CFCF3 are estimated to be 2.5 and 2.1, respectively.