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UV absorption spectrum, and kinetics and mechanism of the self reaction of CF3CF2O2 radicals in the gas phase at 295 K

✍ Scribed by Jens Sehested; Thomas Ellermann; Ole John Nielsen; Timothy J. Wallington; Michael D. Hurley

Publisher: John Wiley and Sons
Year: 1993
Tongue: English
Weight: 950 KB
Volume: 25
Category: Article
ISSN: 0538-8066
DOI: 10.1002/kin.550250903

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✦ Synopsis

The ultraviolet absorption spectrum, kinetics, and mechanism of the self reaction of CF3CF202 radicals have been studied in the gas phase a t 295 K. Two techniques were used; pulse radiolysis W absorption to measure the spectrum and kinetics, and long-path length FTIR spectroscopy to identify and quantify the reaction products. Absorption cross sections were quantified over the wavelength range 220-270 nm. At 230 nm, O C F ~C F ~O ~ = (2.74 t 0.46) X lo-'* cm2 molecule-'. This absorption cross section was used to derive the observed selfreaction rate constant for reaction(l1, defined as, -d[CF3CFzOzYdt = 2kloi,,[CF3CF202]2 :

(1)

The observed products following the self reaction of CF3CF202 radicals were COF2, CF303CF3, CF303C2F5, and CF30H. CF302CF3 was tentatively identified as a product. The carbon balance was 90-100%. The self reaction of CF3CF202 radicals was found to proceed via one channel to produce CF3CF20 radicals which then decompose to give CF3 radicals and COF2. In the presence of 02, CF3 radicals are converted into CF3O radicals. CF3O radicals have several fates; self reaction to give CF302CF3; reaction with CF3O2 radicals to give CF303CF3; reaction with C2F5O2 radicals to give CF303C2F5; or reaction with CF3CF2H to give CF30H.

As part of this work a rate constant of (2.5 2 0.6) X cm3 molecule-s-' was measured for the reaction of C1 atoms with CF3CHF2 using a relative rate technique.

Results are discussed with respect to the atmospheric chemistry of CF3CF2H (HFC-125).

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