Rate constants for the reactions of Br atoms with a series of alkanes, alkenes, and alkynes in the presence of O2

Abstract

AbstractRate 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 N2 + O2 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 O2 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: cm3 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 cm3 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 H2O2. Bromoacetaldehyde was observed as an primary product in the reaction of Br with ethene. Other observed products included CO, CO2, HBr, HOBr, BrCHO, bromoethanol, and probably bromoacetic acid.