Kinetic Study of OH Radical Reactions with CF₃CClCCl₂, CF₃CClCClCF₃ and CF₃CF=CFCF₃

Abstract

The relative rate technique has been used to determine the rate constants of the reactions of OH radicals with CF(3)CCl=CCl(2) (k(1)), CF(3)CCl=CClCF(3) (k(2)) and CF(3)CF=CFCF(3) (k(3)). Experiments were carried out at (298±2) K and atmospheric pressure using ultrapure nitrogen as gas bath. The decay rates of the organic species were measured relative to those of ethane, methanol, acetone, chloroethane and 2-butanone. The following rate constants were derived in units of cm(3) molecule(-1) s(-1): k(1)= (10±1)×10(-13), k(2)=(2.1±0.2)×10(-13) and k(3)=(3.7±0.2)×10(-13). This is the first experimental determination of k(1) and k(2). The rate constants obtained are compared with previous literature data to establish reactivity trends and are used to estimate the atmospheric lifetimes of the studied perhaloalkenes. From the calculated lifetimes, using an average global concentration of hydroxyl radicals, the atmospheric loss of these compounds by the OH-initiated oxidation was determined. Also, estimations have been made of the ozone depletion potential (ODP), the radiative forcing efficiency (RE), the halocarbon global warming potential (HGWP) and the global warming potential (GWP) of the perhaloalkenes. The approximate nature of these values is stressed considering that these are short-lived compounds for which these atmospheric parameters may vary according to latitude and season.

Global warming potentials and radiative efficiencies of halocarbons and related compounds: A comprehensive review

“…Considering that Cometto et al . [] estimated a lifetime of only 31 days for CF 3 CF = CFCF 3 , we think that the lifetime from Vasekova et al . [] may be too long and instead use a value of 31 days when applying the lifetime correction and calculating the GWP value.…”

“…Previous reports of RE of perfluorobut‐2‐ene are in the range of 0.30–0.32 W m −2 ppb −1 (mean: 0.31 W m −2 ppb −1 ) [ Cometto et al ., ; Young et al ., ]. We calculate a RE value of 0.07 W m −2 ppb −1 when using the absorption spectra and lifetime estimate (31 days) from Cometto et al .…”

“…We calculate a RE value of 0.07 W m −2 ppb −1 when using the absorption spectra and lifetime estimate (31 days) from Cometto et al . [], and accounting for stratospheric temperature adjustment and non‐homogeneous distribution.…”

“…The only lifetime reported in the literature for this compound is 1.0 year from Vasekova et al [2006] who refer to a non-traceable source. Considering that Cometto et al [2010] estimated a lifetime of only 31 days for CF 3 CF = CFCF 3 , we think that the lifetime from Vasekova et al [2006] may be too long and instead use a value of 31 days when applying the lifetime correction and calculating the GWP value. 4.1.6.12.…”

“…[211] Previous reports of RE of perfluorobut-2-ene are in the range of 0.30-0.32 W m À2 ppb À1 (mean: 0.31 W m À2 ppb À1 ) [Cometto et al, 2010;Young et al, 2009a]. We calculate a RE value of 0.07 W m À2 ppb À1 when using the absorption spectra and lifetime estimate (31 days) from Cometto et al [2010], and accounting for stratospheric temperature adjustment and nonhomogeneous distribution. 4.1.6.22.…”