Journal of Physical Chemistry, Vol.99, No.46, 16932-16938, 1995
Atmospheric Chemistry of Pentachloroethane (Ccl3Ccl2H) - Absorption-Spectra of Ccl3Ccl2 and Ccl3Ccl2O2 Radicals, Kinetics of the Ccl3Ccl2O2+no Reaction, and Fate of the Ccl3Ccl2O Radical
The absorption spectra of CCl3CCl2 and CCl3CCl2O2 radicals and the rate constant for the reaction of CCl3CCl2O2 radicals with NO were measured at 296 +/- 2 K using a pulse radiolysis technique. The absorption spectra were measured over the wavelength range 220-400 nm. At 230 nm sigma(CCl3CCl2) = (271 +/- 84) X 10(-20) cm(2) molecule(-1), and at 240 nm sigma(CCl3CCl2O2) = (145 +/- 21) X 10(-20) cm(2) molecule(-1). The reaction of F atoms with CCl3CCl2H was determined to have a rate constant of (2.3 +/- 1.6) X 10(-12) cm(3) molecule(-1) s(-1). The reaction of CCl3CCl2O2 with NO proceeds with a rate constant of (6.2 +/- 1.6) X 10(-12) cm(3) molecule(-1) s(-1). This reaction gives NO2 and CCl3CCl3O radicals. In the atmosphere, 85% of the CCl3CCl2O radicals eliminate a Cl atom to give CCl3C(O)Cl, and the remaining 15% decompose via C-C bond scission to give CCl3 radicals and COCl2. As part of the present work, relative rate techniques were used to measure rate constants at 296 +/- 2 K for the reactions of Cl and F atoms with CCl3CCl2H of (5.2 +/- 0.7) X 10(-14) and (2.0 +/- 0.5) X 10(-12) cm(3) molecule(-1) s(-1), respectively.
Keywords:GAS-PHASE;PEROXY-RADICALS;SELF-REACTION;HYDROCHLOROFLUOROCARBONS;295-K;HYDROFLUOROCARBONS;SPECTROSCOPY;MECHANISMS;CF3CHCL2;CFCL2CH3