Kinetics for the gas-phase reactions of OH radicals with the hydrofluoroethers CH2FCF2OCHF2, CHF2CHFCF2OCH2CF3, and CF3CHFCF2OCH2CF3, and CF3CHFCF2OCH2CF2CHF2 at 268-308 K

Rate constants were determined for the reactions of OH radicals with the hydrofluoroethers (HFEs) CH2FCF2OCHF2 (k(1)), CHF2CF2OCH2CF3 (k(2)), CF3CHFCF2OCH2CF3 (k(3)), and CF3CHFCF2OCH2CF2CHF2 (k(4)) by using a relative rate method. OH radicals were prepared by protolysis of ozone at UV wavelenghts (>260 nm) in 100 Torr of a HFE-reference-H2O-O-3-O-2-He gas mixture in a 1-m(3) temperature-controlled chamber. By using CH4, CH3CCl3, and CF3CF2CF2OCH3 as the reference compounds, reaction rate constants of OH radicals of k(1) = (1.68(-1.05)(+1.07)) x 10(-) (12) exp[(-1710 +/- 140)/T], k(2) = (1.36(-0.37)(+0.52)) x 10(-12) exp[(-1470 +/- 90)/T], k(3) = (1.67(-0.65)(+1.05)) x 10(-12) exp[(- 1560 +/- 140)/T], and k(4) = (2.39(-0.76)(+1.10)) x 10(-12) exp[(-1560 +/- 110)/T] cm(3) molecule(-1) s(-1) were obtained at 68-308 K. The errors reported are +/-2 SD, and represent precision only. We estimate that the potential systematic errors associated with uncertainties in the reference rate constants add a further 10% uncertainty to the values of k(1)-k(4). The results are discussed in relation to the predictions of Atkinson's structure-activity relationship model. The dominant tropospheric loss process for the HFEs studied here is considered to be by the reaction with the OH radicals, with atmospheric lifetimes of 11.5, 5.9, 6.7, and 4.7 years calculated for CH2FCF2OCHF2, CHF2CF2OCH2CF3, CF3CHFCF2OCH2CF3, and CF3CHFCF2OCH2CF2CHF2, respectively, by scaling from the lifetime of CH3CCl3. (C) 2003 Wiley Periodicals, Inc. Int I Chem Kinet 35: 239-245, 2003.