Abstract
The rate constants k~1~ for the reaction of CF~3~CF~2~CF~2~CF~2~CF~2~CHF~2~ with OH radicals were determined by using both absolute and relative rate methods. The absolute rate constants were measured at 250–430 K using the flash photolysis–laser‐induced fluorescence (FP‐LIF) technique and the laser photolysis–laser‐induced fluorescence (LP‐LIF) technique to monitor the OH radical concentration. The relative rate constants were measured at 253–328 K in an 11.5‐dm^3^ reaction chamber with either CHF~2~Cl or CH~2~FCF~3~ as a reference compound. OH radicals were produced by UV photolysis of an O~3~–H~2~O–He mixture at an initial pressure of 200 Torr. Ozone was continuously introduced into the reaction chamber during the UV irradiation. The k~1~ (298 K) values determined by the absolute method were (1.69 ± 0.07) × 10^−15^ cm^3^ molecule^−1^ s^−1^ (FP‐LIF method) and (1.72 ± 0.07) × 10^−15^ cm^3^ molecule^−1^ s^−1^ (LP‐LIF method), whereas the K~1~ (298 K) values determined by the relative method were (1.87 ± 0.11) × 10^−15^ cm^3^ molecule^−1^ s^−1^ (CHF~2~Cl reference) and (2.12 ± 0.11) × 10^−15^ cm^3^ molecule^−1^ s^−1^ (CH~2~FCF~3~ reference). These data are in agreement with each other within the estimated experimental uncertainties. The Arrhenius rate constant determined from the kinetic data was K~1~ = (4.71 ± 0.94) × 10^−13^ exp[−(1630 ± 80)/T] cm^3^ molecule^−1^ s^−1^. Using kinetic data for the reaction of tropospheric CH~3~CCl~3~ with OH radicals [k~1~ (272 K) = 6.0 × 10^−15^ cm^3^ molecule^−1^ s^−1^, tropospheric lifetime of CH~3~CCl~3~ = 6.0 years], we estimated the tropospheric lifetime of CF~3~CF~2~CF~2~CF~2~CF~2~CHF~2~ through reaction with OH radicals to be 31 years. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 26–33, 2004