FTIR study of the Cl- and Br-atom initiated oxidation of trichloroethylene
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Abstract:
The Cl- and Br- initiated oxidations of CHCl(DOUBLEBOND)CCl2 in 700 torr of air at 296 K have been studied using a Fourier transform infrared spectrometer. Rate constants k(Cl+CHCl(DOUBLEBOND)CCl2)=(7.2±0.8)×10−11 and k(Br+CHCl(DOUBLEBOND)CCl2)=(1.1±0.4)×10−13 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 Br), CHClO, and CCl2O. Combining results obtained for the Cl-initiated oxidation of CHCl2(SINGLEBOND)CHCl2, we deduced that Cl-addition on trichloroethylene occurs via channel 1a, Cl+CHCl(DOUBLEBOND)CCl2→ CHCl2(SINGLEBOND)CCl2, (100±12)%. Self-reaction of the subsequently generated peroxy radicals CHCl2(SINGLEBOND)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(DOUBLEBOND)CCl2→CHBrCl(SINGLEBOND)CCl2 (17a) accounted for ≥(96±11)% of the total reaction. Decomposition of the CHBrCl(SINGLEBOND)CCl2O radicals proceeds (≥93±11)% via CHBrClC(O)Cl+Cl. As part of this work, k(Cl+CHCl2C(O)Cl)=(3.6±0.6)×10−14 and k(Cl+CHCl2(SINGLEBOND)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. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet: 29: 695–704, 1997.