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 rat e constant for the reaction of CCl3CCl2O2 radicals with NO were measur ed at 296 +/- 2 K using a pulse radiolysis technique. The absorption s pectra were measured over the wavelength range 220-400 nm. At 230 nm s igma(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 cons tant 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 CCl3CC l3O radicals. In the atmosphere, 85% of the CCl3CCl2O radicals elimina te 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 prese nt 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.