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Abstract

Rate coefficients for the reactions of CH3 + Br2 (k2), CH3CO + Br2 (k3), and Cl + Br2 (k5) were measured using the laser-pulsed photolysis method combined with detection of the product Br atoms using resonance fluorescence. For the reactions involving organic radicals, the rate coefficients were observed to increase with decreasing temperature and within the temperature range explored, were adequately described by Arrhenius-like expressions: k2 (224–358 K) = 1.83 × 10−11 exp(252/T) and k3 (228–298 K) = 2.92 × 10−11 exp(361/T) cm3 molecule−1 s−1. The total, temperature-independent uncertainty for each reaction (including possible systematic errors in Br2 concentration measurement) was estimated as ∼7% for k2 and 10% for k3. Accurate data on k5 was obtained at 298 K, with a value of 1.88 × 10−10 cm3 molecule−1 s−1 obtained (with an associated error of 6%). A limited data set at 228 K suggests that k5 is, within experimental uncertainty, independent of temperature. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 575–585, 2010