Rate constants for the reactions of Br atoms with a series of alkanes, alkenes, and alkynes in the presence of O 2

Rate constants of Br atom reactions have been determined using a relative kinetic method in a 20 l reaction chamber at total pressures between 25 and 760 torr in N 2 + O 2 diluent over the temperature range 293–355 K. The measured rate constants for the reactions with alkynes and alkenes showed dependence upon temperature, total pressure, and the concentration of O 2 present in the reaction system. Values of (6.8 ± 1.4) × 10 −15 , (3.6 ± 0.7) × 10 −14 , (1.5 ± 0.3) × 10 −12 , (1.6 ± 0.3) × 10 −13 , (2.7 ± 0.5) × 10 −12 , (3.4 ± 0.7) × 10 −12 , and (7.5 ± 1.5) × 10 −12 (units: cm 3 s −1 ) have been obtained as rate constants for the reactions of Br with 2,2,4‐trimethylpentane, acetylene, propyne, ethene, propene, 1‐butene, and trans ‐2‐butene, respectively, in 760 torr of synthetic air at 298 K with respect to acetaldehyde as reference, k = 3.6 × 10 −12 cm 3 s −1 . Formyl bromide and glyoxal were observed as primary products in the reaction of Br with acetylene in air which further react to form CO, HBr, HOBr, and H 2 O 2 . Bromoacetaldehyde was observed as an primary product in the reaction of Br with ethene. Other observed products included CO, CO 2 , HBr, HOBr, BrCHO, bromoethanol, and probably bromoacetic acid.