Ultraviolet Absorption Spectrum and Kinetics and Mechanism of the Self-Reaction of CHF2CF2O2 Radicals in the Gas Phase at 298 K

Article abstract of DOI:10.1021/j100205a050

The ultraviolet absorption spectrum and kinetics and mechanism of the self-reaction of CHF2CF2O2 radicals have been studied in the gas phase at 298 K.Two techniques were used: pulse radiolysis UV absorption to measure the spectrum and kinetics and long-path-length Fourier transform infrared spectroscopy (FTIR) to identify and quantify the reaction products.Absorption cross sections were quantified over the wavelength range 220-270 nm.At 230 nm, ?_CHF2CF2O2 = (3.2 +/- 0.5) * 10^-18 cm² molecule^-1.Errors are statistical (2 standard deviations) plus our estimate of potential systematic uncertainty (15percent).This absorption cross section was used to derive the observed self-reaction rate constant for the reaction CHF2CF2O2 + CHF2CF2O2 -> products (1), defined as -d/dt = 2k_l,obs². k_l,obs = (2.7 +/- 0.6) * 10^-12 cm³ molecule^-1 s^-1 (errors are 2 standard deviations).Measured UV transients were not corrected for possible complications caused by formation of CHF2O2 and HO2 radicals.Hence, k_l,obs may not be the true bimolecular rate constant for reaction 1.The only carbon-containing product observed by FTIR spectroscopy was COF2.The carbon balance was, within our experimental uncertainty, 100percent.As part of this work, a rate constant of (1.9 +/- 0.2) * 10^-15 cm³ molecule^-1 s^-1 was measured for the reaction of Cl atoms with CHF2CHF2 using a relative rate technique.Results are discussed with respect to the atmospheric chemistry of haloalkanes.