The UV absorption spectra and kinetics of the self reactions of CH₂ClO₂ and CH₂FO₂ radicals in the gas phase

The ultraviolet absorption spectra of chloromethylperoxy and fluoromethylperoxy radicals, CH 2 ClO 2 and CH 2 FO 2 , and the kinetics of their respective self reactions have been studied in the gas phase using a flash photolysis technique. The absorption spectra for both radicals were quantified over the wavelength range 210 and 290 nm. The measured absorption cross‐sections were used to derive the observed self‐reaction rate constants (for reactions 1 and 2) over the temperature range 228–380 K, defined as –d[CH 2 XO 2 ]/dt = 2 k [CH 2 XO 2 ] 2 , where X represents Cl or F. magnified image The rate constants at 298 K were found to be independent of pressure over the range 25–400 torr N 2 with values of k 1 (298 K) = (3.78 ± 0.45) × 10 −12 and k 2 (298 K) = (3.07 ± 0.65) × 10 −12 in units of cm 3 molecule −1 s −1 . The kinetic data over the complete temperature range are represented by the Arrhenius expressions: where the error limits represent 2σ from linear least squares analysis. These results are discussed with respect to previous measurements of the absorption spectra and reactions of alkylperoxy radicals.