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UV absorption spectrum, and kinetics and mechanism of the self reaction of CF 3 CF 2 O 2 radicals in the gas phase at 295 K
Author(s) -
Sehested Jens,
Ellermann Thomas,
Nielsen Ole John,
Wallington Timothy J.,
Hurley Michael D.
Publication year - 1993
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550250903
Subject(s) - radical , chemistry , reaction rate constant , radiolysis , absorption (acoustics) , kinetics , absorption spectroscopy , chemical kinetics , reaction mechanism , photochemistry , analytical chemistry (journal) , organic chemistry , catalysis , physics , quantum mechanics , acoustics
The ultraviolet absorption spectrum, kinetics, and mechanism of the self reaction of CF 3 CF 2 O 2 radicals have been studied in the gas phase at 295 K. Two techniques were used; pulse radiolysis UV 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, σ CF 3 CF 2 O 2= (2.74 ± 0.46) ×10 −18 cm 2 molecule −1 . This absorption cross section was used to derive the observed self reaction rate constant for reaction (1), defined as, − d [CF 3 CF 2 O 2 ]/ dt = 2 k 1obs [CF 3 CF 2 O 2 ] 2 :k 1obs = (2.10 ± 0.38) ×10 −12 cm 3 molecule −1 s −1 (2σ). The observed products following the self reaction of CF 3 CF 2 O 2 radicals were COF 2 , CF 3 O 3 CF 3 , CF 3 O 3 C 2 F 5 , and CF 3 OH. CF 3 O 2 CF 3 was tentatively identified as a product. The carbon balance was 90–100%. The self reaction of CF 3 CF 2 O 2 radicals was found to proceed via one channel to produce CF 3 CF 2 O radicals which then decompose to give CF 3 radicals and COF 2 . In the presence of O 2 , CF 3 radicals are converted into CF 3 O radicals. CF 3 O radicals have several fates; self reaction to give CF 3 O 2 CF 3 ; reaction with CF 3 O 2 radicals to give CF 3 O 3 CF 3 ; reaction with C 2 F 5 O 2 radicals to give CF 3 O 3 C 2 F 5 ; or reaction with CF 3 CF 2 H to give CF 3 OH.As part of this work a rate constant of (2.5 ± 0.6) ×10 −16 cm 3 molecule − s −1 was measured for the reaction of Cl atoms with CF 3 CHF 2 using a relative rate technique.Results are discussed with respect to the atmospheric chemistry of CF 3 CF 2 H (HFC‐125). © 1993 John Wiley & Sons, Inc.