FTIR STUDY OF THE CL-ATOM AND BR-ATOM INITIATED OXIDATION OF TRICHLOROETHYLENE

The Cl- and Br- initiated oxidations of CHCl=CCl2 in 700 torr of air a t 296 K have been studied using a Fourier transform infrared spectrome ter. Rate constants k(Cl + CHCl=CCl2) = (7.2 +/- 0.8) X 10(-11) and k( Br + CHCl=CCl2) = (1.1 + 0.4) X 10(-13) cm(3) 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)C l, (X = Cl or Br), CHClO, and CCl2O. Combining results obtained for th e Cl-initiated oxidation of CHCl2-CHCl2, we deduced that Cl-addition o n trichloroethylene occurs via channel 1a, Cl + CHCl=CCl2 --> CHCl2-CC l2, (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=CCl 2 --> CHBrCl-CCl2 (17a) accounted for greater than or equal to(96 +/- 11)% of the total reaction. Decomposition of the CHBrCl--CCl2O radical s proceeds (greater than or equal to 93 +/- 11)% via CHBrClC(O)Cl + Cl . As part of this work, k(Cl + CHCl2C(O)Cl)= (3.6 +/- 0.6) X 10(-14) a nd k(Cl + CHCl2-CHCl2) = (1.9 +/- 0.2) x 10(-13) cm(3) molecule(-1) s( -1) were measured. Errors reported above include statistical uncertain ties (2 sigma) and estimated systematic uncertainties. (C) 1997 John W iley & Sons, Inc.