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

The relative rate technique has been used to determine the rate constants of the reactions of OH radicals with CF3CCl=CCl2 (k(1)), CF3CCl=CClCF3 (k(2)) and CF3CF=CFCF3 (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) x 10(-13), k(2)=(2.1 +/- 0.2) x 10(-13) and k(3)=(3.7 +/- 0.2) x 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.