Atmospheric chemistry of CH2BrCl: Kinetics and mechanism of the reaction of F atoms with CH2BrCl and fate of the CHBrClO center dot radical

The reaction of F atoms with CH2BrCl was studied using a pulsed radiolysis technique and found to proceed via two channels: direct hydrogen abstraction and adduct formation. The adduct exists in equilibrium with F atoms and CH2BrCl. The equilibrium constant K-4 = [Adduct]/([CH2BrCl][F]) (4.2 +/- 1.0) x 10(-16) cm(3)molecule(-1). In 1000 mbar total pressure of SF6 at 294 +/- 2 K, the yield of the adduct is 68 +/- 11% and the overall rate constant for reaction of F atoms with CH2BrCl is k(4) (1000 mbar) = (3.6 +/- 0.9) x 10(-11) cm(3) molecule(-1) s(-1). The adduct reacts with NO with a rate constant of (2.09 +/- 0.41) x 10(-11) cm(3) molecule(-1) s(-1). The atmospheric fate of the alkoxy radical CHBrClO is Br atom elimination, which occurs at a rate estimated to be >2 x 10(6) s(-1) in 700 Torr of air at 295 K. Relative rate techniques were used to measure k(Cl + CH2BrCl) = (4.2 +/- 0.5) x 10(-13) and k(F + CH2BrCl --> CHBrCl + HF) = (1.2 +/- 0.4) x 10(-11) cm(3) molecule(-1) s(-1). These results are compared to the available literature data.