38282-29-0Relevant academic research and scientific papers
Temperature-dependent rate coefficient measurements for the reaction of bromine atoms with trichloroethene, ethene, acetylene, and tetrachloroethene in air
Ramacher, Bjoern,Orlando, John J.,Tyndall, Geoffrey S.
, p. 198 - 211 (2007/10/03)
In this article, rate coefficients for the reaction of Br atoms with a series of unsaturated species (trichloroethene, k1; ethene, k2; acetylene, k3; and tetrachloroethene, k4) are reported in 700 Torr air over the temperature range 228-298 K. The data were obtained in a temperature-regulated environmental chamber/FTIR spectrometer system, using standard relative rate techniques, with the reaction of Br with CH2O and CH3CHO as the reference reactions. Room-temperature values for k1 through k4 were found to be 1.56×10-13, 1.23×10-13, 2.86×10-14, and -16 cm3 molecule-1 s-1, respectively, in reasonable accord with previously available data. At 240 K, values of k1 = 1.77×10-12, k2 = 5.76×10-13, k3 = 3.97×10-14, and k4 = 3.22×10-15 cm3 molecule-1 s-1 are reported. These k2 and k3 values are 2-3 times lower than those currently in use, which are obtained by extrapolation of previous measurements made over the range 298-350 K. An investigation of the mechanism of the Br-atom-initiated oxidation of acetylene, trichloroethene, and tetrachloroethene was also conducted as a function of temperature. Although no temperature dependence to the product yields was observed for any of the systems studied, the product distributions were found to be altered by the presence of NOx in the case of trichloroethene and tetrachloroethene. An anomalously low rate coefficient for the reaction of Br with glyoxal (HC(O)CHO, a product of acetylene oxidation), k17 = 1.1×10-14 cm3 molecule-1 s-1, is also reported.
FTIR study of the Cl- and Br-atom initiated oxidation of trichloroethylene
Catoire,Ariya,Niki,Harris
, p. 695 - 704 (2007/10/03)
The Cl- and Br- initiated oxidations of CHCl=CCl2 in 700 torr of air at 296 K have been studied using a Fourier transform infrared spectrometer. Rate constants k(Cl + CHCl=CCl2) = (7.2 ± 0.8) × 10-1 and k(Br + CHCl=CCl2) = (1.1 ± 0.4) × 1013 cm3 molecule-1 s-1 were determined using a relative rate technique with ethane and ethylene as references, respectively. The major products observed were CHXClC(O)Cl, (X = Cl or Bl), CHClO, and CCl2O. Combining results obtained for the Cl-initiated oxidation of CHCl2 - CHCl2, we deduced that Cl-addition on trichloroethylene occurs via channel 1a, Cl + CHCl=CCl2 → CHCl2-CCl2, (100 ± 12)%. Self-reaction of the subsequently generated peroxy radicals CHCl2-CCl2O2 leads to CHCl2CCl2O radicals which were found to decompose via channel 8a, CHCl2C(O)Cl + Cl, (91 ± 11)% of the time, and channel 8b, CHCl2 + CCl2O. (9 ± 2)%. The reaction Br + CHCl=CCl2 → CHBrCl-CCl2 (17a) accounted for ≥(96 ± 11)% of the total reaction. Decomposition of the CHBrCl-CCl2O radicals proceeds (≥93 ± 11)% via CHBrClC(O)Cl + Cl. As part of this work, k(Cl + CHCl2C(O)Cl) = (3.6 ± 0.6) × 10-14and k(Cl + CHCl2-CHCl2) = (1.9 ± 0.2) × 10-13 cm3 molecule-1 s-1 were measured. Errors reported above include statistical uncertainties (2σ) and estimated systematic uncertainties.
