Atmospheric lifetimes, infrared spectra and degradation products of a series of hydrofluoroethers

The rate constants of the reactions between the OH radical and a series of hydrofluoroethers (HFE) have been measured. The reaction of OH with CHF2OCF2OCHF2 (1), CHF2OCF2CF2OCHF2 (2), CHF2OCF2CF2OCF2OCHF2 (3) and CH3OC4F9 (4) were investigated at 295±3 K and 740±5 Torr total pressure. The following values of the rate constants were determined for the reaction with the OH radical: k1=(2.4±0.7)×10-15 cm3 molecule-1 s-1, k2=(4.7±1.6)×10-15 cm3 molecule-1 s-1, k3=(4.6±1.6)×10-15 cm3 molecule-1 s-1 and k4=(7.2±1.6)×10-15 cm3 molecule-1 s-1. (All values are given with 2σ uncertainties). Infrared spectra were obtained for all four HFEs in the range from 600 to 4000 cm-1 (3 to 17 μm), with the following IBI-values (integrated band intensities): IBI1= (5.19±0.23)×10-16 cm molecule-1 for the 978–1584 cm-1 band, IBI2=(6.04±0.13)×10-16 cm molecule-1 for the 930–1501 cm-1 band, IBI3=(8.49±0.34)×10-16 cm molecule-1 from the 963–1587 cm-1 band and IBI4=(4.23±0.14)×10-16 cm molecule-1 for the 845–1428 cm-1 band. Carbonyl fluoride, CF2O, was the only fluorine-containing degradation product that was found from the Cl atom-initiated reactions of both CHF2OCF2OCF2CF2OCHF2 and CH3OC4F9, with measured product yields of 60–97% and 20–40% (based on carbon atoms), respectively. Due to the high uptake parameter of CF2O to liquid water, its lifetime in the atmosphere is very short (with an upper limit between 15 and 30 d). It is rapidly incorporated into raindrops/aerosols, where it eventually degrades to HF and CO2. The GWP of CF2O is therefore negligible compared to those of CFC-11 and CFC-12.