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Rate Constants for the Reactions between OH and Perfluorinated Alkenes

Orkin, V. L., G. A. Poskrebyshev, and M. J. Kurylo (2011), Rate Constants for the Reactions between OH and Perfluorinated Alkenes, J. Phys. Chem. A, 115, 6568-6574, doi:10.1021/jp201663j.

The rate constants for the reactions of OH radicals with fully fluorinated alkenes containing different numbers of -CF3 groups next to olefinic carbon, CF2=CF2, CF2=CFCF3, CF3CF=CFCF3, and (CF3)2C=CFC2F5, were measured between 230 and 480 K using the flash photolysis resonance fluorescence technique to give the following expressions:
kC2F4(250-480 K) = 1.32 × 10-12 × (T/298 K)^0.9 × exp(+600 K/T) cm3 molecule-1 s-1,
kC3F6(230-480 K) = 9.75 × 10-14 × (T/298 K)^1.94 × exp(+922 K/T) cm3 molecule-1 s-1,
ktrans-C4F8(230-370 K) = 7.50 × 10 × (T/298 K)^1.68 × exp(+612 K/T) cm3 molecule-1 s-1,
kcis-C4F8(230-370 K) = 2.99 × 10-14 × (T/298 K)^2.61 × exp(+760 K/T) cm3 molecule-1 s-1, and
kC6F12(250-480 K) = 2.17 × 10-15 × (T/298 K)^3.90 × exp(+1044 K/T) cm3 molecule-1 s-1.
The kinetics of the OH reaction in an industrial sample of octofluoro-2-propene (a mixture of the cis- and trans-isomers of CF3CF=CFCF3) was studied to determine the “effective” reaction rate constant for the typically industrial mixture: k<C4F8>(230-480 K) = 7.89 × 10-14 × (T/298 K)^1.71 × exp(+557 K/T) cm3 molecule-1 s-1. On the basis of these results, the atmospheric lifetimes were estimated to be 1.2, 5.3, 21, 34, and 182 days for CF2=CF2, CF3CF=CF2, trans-CF3CF=CFCF3, cis-CF3CF=CFCF3, and (CF3)2C=CFC2F5, respectively. The general pattern of halolalkene reactivity toward OH is discussed.

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Upper Atmosphere Research Program (UARP)