ATMOSPHERIC LIFETIMES, INFRARED-SPECTRA AND DEGRADATION PRODUCTS OF ASERIES OF HYDROFLUOROETHERS

The rate constants of the reactions between the OH radical and a serie s of hydrofluoroethers (HFE) have been measured. The reaction of OH wi th CHF2OCF2OCHF2 (1), CHF2OCF2CF2OCHF2 (2), CHF2OCF2CF2OCF2OCHF2 (3) a nd CH3OC4F9, (4) were investigated at 295 +/- 3 K and 740 +/- 5 Torr t otal pressure. The following values of the rate constants were determi ned for the reaction with the OH radical: k(1) = (2.4 +/- 0.7) x 10(-1 5) cm(3) molecule(-1) s(-1), k(2) = (4.7 +/- 1.6) x 10(-15) cm(3) mole cule(-1) s(-1) k(3) = (4.6 +/- 1.6) x 10(-15) cm(3) molecule(-1) s(-1) and k(4) = (7.2 +/- 1.6)x 10(-15) cm(3) molecule(-1) s(-1). (All valu es are given with 2 sigma uncertainties). Infrared spectra were obtain ed for all four HFEs in the range From 600 to 4000 cm(-1) (3 to 17 mu m), with the following IBI-values (integrated band intensities): IBI1 = (5.19 +/- 0.23) x 10(-16) cm molecule(-1) for the 978-1584 cm(-1) ba nd, IBI2 = (6.04 +/- 0.13) x 10(-16) cm molecule(-1) for the 930-1501 cm(-1) band, IBI3 =(8.49 +/- 0.34)x 10(-16) cm molecule(-1) from the 9 63-1587 cm(-1) band and IBI4 = (4.23 +/- 0.14)x 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 ato m-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 be tween 15 and 30 d). It is rapidly incorporated into raindrops/aerosols , where it eventually degrades to HF and CO2. The GWP of CF2O is there fore negligible compared to those of CFC-11 and CFC-12. (C) 1998 Elsev ier Science Ltd. All rights reserved.