The UV absorption spectra of CH2Br and CH2BrO2 and the reaction kinetics of CH2BrO2 with itself and with HO2 at 298 K

The UV absorption spectra of the bromomethyl (CH2Br) and bromomethylperoxy (CH2BrO2) radicals have been determined using the flash photolysis 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 coefficients were determined at 298 K for the self-reaction (CH2BrO2BrO2 + CH2BrO2 → 2 CH2BrO + O2 (3), k3 = (1.05 ± 0.4) × 10−12 cm3 molecule−1 s−1) and for the reaction with HO2 (CH2BRO2 + HO2 → products (5), k5 = (6.7 ± 3.8) × 10−12 cm3 molecule−1 s−1). As for fluorine and chlorine substitution, bromine substitution enhances the rate constant of the self-reaction, compared to that of the methylperoxy radical, whereas it does not significantly change the rate constant for the reaction with HO2.