ATMOSPHERIC CHEMISTRY OF HFC-152 - UV ABSORPTION-SPECTRUM OF CH2FCFHO2 RADICALS, KINETICS OF THE REACTION CH2FCFHO2-]CH2FCRFO+NO2, AND FATEOF THE ALKOXY RADICAL CH2FCFHO(NO)

The ultraviolet absorption spectrum of CH2FCFHO2 radicals and the kine tics and mechanism of their reaction with NO have been studied in the gas phase at 296 K using a pulse radiolysis technique. A long path-len gth Fourier transform infrared technique was used to study the atmosph eric fate of CH2FCFHO radicals. Absorption cross sections were quantif ied over the wavelength range 220-300 nm. At 240 nm, sigma(CH2FCFHO2) (3.28 +/- 0.40) x 10(-18) cm(2) molecule(-1). Errors are statistical ( 2 standard deviations) plus our estimate of potential systematic uncer tainty (10%). Monitoring the rate of NO2 formation using a monitoring wavelength of 400 nm allowed a lower limit of kappa(3) > 8.7 x 10(-12) cm(3) molecule(-1) s(-1) to be derived for the reaction of CH2FCFHO2 radicals with NO. The alkoxy radical CH2FCFHO was found to undergo C-C bond scission rapidly with a rate greater than 6 X 10(4) s(-1). The C l-atom-initiated oxidation of HFC-152 in air in the presence of NOx ga ve HC(O)F as the sole carbon-containing product. The carbon balance wa s 91 +/- 10%. Results are discussed with respect to the atmospheric ch emistry of HFC-152. As part of the present work, a relative rate techn ique was used to measure rate constants of (6.7 +/- 0.8) x 10(-13) and (3.8 +/- 1.1) x 10(-11) cm(3) molecule(-1) s(-1) for the reaction of CH2FCH2F with Cl and F atoms, respectively.