Study of the OH and Cl-Initiated Oxidation, IR Absorption Cross-Section, Radiative Forcing, and Global Warming Potential of Four C4-Hydrofluoroethers

Abstract

Infrared absorption cross-sections and OH and Cl reaction rate coefficients for four C4-hydrofluoroethers (CF3)2CHOCH3, CF3CH2OCH2CF3, CF3CF2CH2OCH3, and CHF2CF2CH2OCH3 are reported. Relative rate measurements at 298 K and 1013 hPa of OH and Cl reaction rate coefficients give k(OH+(CF3)2CHOCH3) = (1.27 ± 0.13) × 10-13, k(OH+CF3CH2OCH2CF3) = (1.51 ± 0.24) × 10-13, k(OH+CF3CF2CH2OCH3) = (6.42 ± 0.33) × 10-13, k(OH+CHF2CF2CH2OCH3) = (8.7 ± 0.5) × 10-13, k(Cl+(CF3)2CHOCH3) = (8.4 ± 1.3) × 10-12, k(Cl+CF3CH2OCH2CF3) = (6.5 ± 1.7) × 10-13, k(Cl+CF3CF2CH2OCH3) = (4.0 ± 0.8) × 10-11, and k(Cl+CHF2CF2CH2OCH3) = (2.65 ± 0.17) × 10-11 cm3 molecule-1 s-1. The primary products of the OH and Cl reactions with the fluorinated ethers have been identified as esters, and OH and Cl reaction rate coefficients for one of these, CF3CH2OCHO, are reported: k(OH+CF3CH2OCHO) = (7.7 ± 0.9) × 10-14 and k(Cl+CF3CH2OCHO) = (6.3 ± 1.9) × 10-14 cm3 molecule-1 s-1. The rate coefficient for the Cl-atom reaction with CHF2CH2F is derived as k(Cl+CHF2CH2F) = (3.0 ± 0.9) × 10-14 cm3 molecule-1 s-1 at 298 K. The error limits include 3σ from the statistical data analyses as well as the errors in the rate coefficients of the reference compounds employed. The tropospheric lifetimes of the hydrofluoroethers are estimated to be short τOH((CF3)2CHOCH3) 100 days, τOH(CF3CH2OCH2CF3) 80 days, τOH(CF3CF2CH2OCH3) 20 days, and τOH(CHF2CF2CH2OCH3) 14 days, and their global warming potentials are small compared to CFC-11.