Kinetics for the gas‐phase reactions of OH radicals with the hydrofluoroethers CH₂FCF₂OCHF₂, CHF₂CF₂OCH₂CF₃, CF₃CHFCF₂OCH₂CF₃, and CF₃CHFCF₂OCH₂CF₂CHF₂ at 268–308 K

Abstract

Abstract Rate constants were determined for the reactions of OH radicals with the hydrofluoroethers (HFEs) CH 2 FCF 2 OCHF 2 ( k 1 ), CHF 2 CF 2 OCH 2 CF 3 ( k 2 ), CF 3 CHFCF 2 OCH 2 CF 3 ( k 3 ), and CF 3 CHFCF 2 OCH 2 CF 2 CHF 2 ( k 4 ) by using a relative rate method. OH radicals were prepared by photolysis of ozone at UV wavelengths (>260 nm) in 100 Torr of a HFE–reference–H 2 O–O 3 –O 2 –He gas mixture in a 1‐m 3 temperature‐controlled chamber. By using CH 4 , CH 3 CCl 3 , CHF 2 Cl, and CF 3 CF 2 CF 2 OCH 3 as the reference compounds, reaction rate constants of OH radicals of k 1 = (1.68 ) × 10 −12 exp[(−1710 ± 140)/ T ], k 2 = (1.36 ) × 10 −12 exp[(−1470 ± 90)/ T ], k 3 = (1.67 ) × 10 −12 exp[(−1560 ± 140)/ T ], and k 4 = (2.39 ) × 10 −12 exp[(−1560 ± 110)/ T ] cm 3 molecule −1 s −1 were obtained at 268–308 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 CH 2 FCF 2 OCHF 2 , CHF 2 CF 2 OCH 2 CF 3 , CF 3 CHFCF 2 OCH 2 CF 3 , and CF 3 CHFCF 2 OCH 2 CF 2 CHF 2 , respectively, by scaling from the lifetime of CH 3 CCl 3 . © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 239–245, 2003