CHEMICAL IONIZATION MASS-SPECTROMETRIC STUDIES OF THE GAS-PHASE REACTIONS CF3O2+NO, CF3O+NO, AND CF3O+RH

We have used a flow tube reactor coupled to a chemical ionization mass spectrometric (CIMS) detector to study the reactions of trifluoromethylperoxy (CF3O2) and trifluoromethoxy (CF3O) radicals with NO and the reaction of CF3O with isobutane. We have determined the rate coefficient at 297 K for the reaction CF3O2 + NO to be (1.53 +/- 0.20) x 10(-11) cm3 molecule-1 s-1 (all uncertainties are for 95% confidence limits), in excellent agreement with two previous measurements. The use of the CIMS detection technique has allowed us to observe both CF3O and NO2 as the products of this reaction. Modeling of a secondary reaction between CF3O and NO observed in these studies has yielded an estimate of k = (2 +/- 1) X 10(-11) cm3 molecule-1 s-1 for this reaction, in which FNO was observed as a product. A relatively rapid reaction was also observed between CF3O and isobutane, for which a rate coefficient of (5 +/- 3) x 10(-12) cm3 molecule-1 s-1 is estimated. This reaction was seen to proceed by hydrogen abstraction, yielding trifluoromethanol, CF3OH. A much slower H-abstraction reaction was observed between CF3O and methane. The significance of these reactions for the atmospheric fate of the trifluoromethoxy radical is discussed.