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UV absorption spectra and kinetics of the self reaction of CFCl 2 CH 2 O 2 and CF 2 ClCH 2 O 2 radicals in the gas phase at 298 K
Author(s) -
Wallington Timothy J.,
Nielsen Ole J.
Publication year - 1991
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.550230905
Subject(s) - chemistry , radiolysis , radical , kinetics , reaction rate constant , absorption spectroscopy , absorption (acoustics) , analytical chemistry (journal) , chemical kinetics , absorption cross section , spectral line , cross section (physics) , organic chemistry , optics , physics , quantum mechanics , astronomy
The ultraviolet absorption spectra of the peroxy radicals derived from hydrochlorofluorocarbons 141b and 142b, (CFCl 2 CH 2 O 2 and CF 2 ClCH 2 O 2 , respectively), and the kinetics of their self reactions have been studied in the gas phase at 298 K using a pulse radiolysis technique. Absorption cross sections were quantified over the wavelength range 220–300 nm. Measured absorption cross sections at 250 nm were indistinguishable within the experimental uncertainties (≈10%) and yield;\documentclass{article}\pagestyle{empty}\begin{document}$$ \sigma _{{\rm CFCl2CH2O2}} (250{\rm\, nm) =\,}\sigma _{{\rm CF2ClCH2O2}} (250{\rm\, nm) = (3}{\rm .38}\, \pm\, {\rm 0}{\rm .68)}\, \times\, {\rm 10}^{- 18}\, {\rm cm}^{\rm 2}\, {\rm molecule}^{- 1} $$\end{document} Errors represent the sum of statistical uncertainty and our estimate of potential systematic errors. Our absorption cross section data were then used to derive the observed self reaction rate constants for reactions (1) and (2), defined as − d [RO 2 ]/ dt = 2k[RO 2 ] 2 (R = CFCl 2 CH 2 or CF 2 ClCH 2 ),of k 1obs = (4.36 ± 0.64) × 10 −12 and k 2obs = (4.13 ± 0.58) × 10 −12 cm 3 molecule −1 s −1 , quoted errors represent 2σ. These results are discussed with respect to previous studies of the absorption spectra and kinetics of peroxy radicals.