THE UV ABSORPTION-SPECTRA OF CH2BR AND CH2BRO2 AND THE REACTION-KINETICS OF CH2BRO2 WITH ITSELF AND WITH HO2 AT 298K

The UV absorption spectra of the bromomethyl (CH2Br) and bromomethylpe roxy (CH2BrO2) radicals have been determined using the flash photolysi s technique. CH2Br exhibits the typical absorption band of halomethyl radicals, peaking near 230 nm, and CH2BrO2 exhibits the typical broad absorption of peroxy radicals, with a maximum at 240 nm. Rate coeffici ents were determined at 298 K for the self-reaction (CH2BrO2BrO2 --> C H2BrO2 --> 2 CH2BrO2 + O-2 (3), k(3) = (1.05 +/- 0.4) X 10-(12) cm(3) molecule(-1) s(-1)) and for the reaction with HO2 (CH2BrO2 + HO2 --> p roducts (5), k(5) = (6.7 +/- 3.8) x 10-(12) cm(3) molecule(-1) s(-1)). As for fluorine and chlorine substitution, bromine substitution enhan ces the rate constant of the self-reaction, compared to that of the me thylperoxy radical, whereas it does not significantly change the rate constant for the reaction with HO2.