Lb. Tichenor et al., Kinetic and modeling studies of the reaction of hydroxyl radicals with tetrachloroethylene, J PHYS CH A, 104(8), 2000, pp. 1700-1707
Rate coefficients are reported for the gas-phase reaction of the hydroxyl r
adical (OH) with. C2Cl4 (k(l)) over an extended temperature range at 740 +/
- 10 Torr in a He bath gas. These absolute rate measurements were conducted
using a laser photolysis/laser-induced fluorescence (LP/LIF) technique und
er slow flow conditions. The lower temperature values for k(l) are within /-2 sigma of previous data using different techniques. The overall slope of
our Arrhenius plot varies slightly from previously reported values. Agreem
ent within our own data holds up to similar to 720 K, but reliable measurem
ent beyond this temperature was hampered by apparent thermal decomposition
of our OH source (HONO). An Arrhenius fit to the data yielded the expressio
n k(1)(T) = (1.68 +/- 0.25) x 10(-12) exp(-764.2 +/- 79.1/T), whereas a thr
ee-parameter Arrhenius fit yielded the expression k(l)(T) (1.93 +/- 0.20) x
10(-22)(T)(3.2) exp(660.8 +/- 54.6/T), where k is in units of cm(3) molecu
le(-1) s(-1). This work shows some deviation from previous low-temperature
data. We propose that surface absorption influenced previously measured rat
e constants. Significant absorption was evident at low temperatures, and an
experimental technique was developed to negate this effect. The predicted
mechanisms were conceptualized using ab initio calculations to define the a
ctivated complex and transient intermediates, and thus predict the most lik
ely path and products. Quantum RRK analysis yielded no overall pressure dep
endence. Model predictions indicate that: trichloroethenol formation via Cl
elimination dominates up to temperatures of 2000 K. At flame temperatures,
the analysis also predicts increased formation of trichloroacetyl chloride
with hydrogen elimination and back reaction to the original reactants.