The kinetics of the reaction of the CF3O radical with NO2 has been studied at 298 K at low pressure (0.5-9 Ton of helium) by fast-low-laser-induced fluorescence (LIF), pyrolysis of a dilute mixture of CF3OOCF3 and He being used as the source of the CF3O radical. In good agreement with the results of Zellner and co-workers (obtained in the pressure range 5-100 Ton), the rate constant has been found to be pressure dependent. All the experimental data were analysed by a multichannel RRKM procedure using the results of ab initio calculations as input data. This revealed that two reaction channels, the association CF3O +/- NO2 --> CF3ONO2 (1a) and the disproportionation CF3O + NO2 --> CF2O + FNO2 (1b), must be invoked and they proceed via a common energized adduct CF3ONO2*. The pressure dependence of the branching ratio was predicted by this calculation: the disproportionation channel would be negligible near atmospheric pressure and becomes the major channel at pressure below ca. 0.3 Torr, with a calculated second-order limiting low-pressure value of the rate equal to 3.2 x 10(-12) cm(3) molecule(-1) s(-1). The high-pressure limit rate constant obtained is k(infinity) = (1.65 +/- 0.2) x 10(-11) cm(3) molecule(-1) s(-1). An analytical representation of the pressure dependence of the rate constant at 298 K is proposed using the conventional Tree expression with an added constant.

The rate constant k(5) of the reaction R(5) : CF3O + O-3 --> products has been measured at room temperature with the absolute Fast Flow tube technique in the pressure range 2-9 Torr. The CF3O radicals are generated by pyrolysis of the dimer CF3OOCF3 and their relative concentration is followed by Laser Induced Fluorescence. The CF3O/He mixture is flowed through the movable central injector whereas the reactant (ozone) is flowed into the main flow tube; this protocol allows a better control of the side reactions which compete with R(?)5. The average of our measurements leads to: k(5) = (1.3 +/- 0.5) x 10(-14) cm(3) molec(-1) s(-1) which is in reasonable agreement with the more recent determinations.

The rate constants for the reactions CF3O2 + NO → CF3O + NO2 (1) and CF3O + NO → products (2) have been measured at room temperature using a fast flow reactor associated with a monitoring of CF3O radicals by laser induced fluorescence (LIF); for the measurement of k1, CF3O radicals are prepared by the discharge flow technique in the reactive system F/CF3H/O2/NO; the average value is k1 = (1.76 ± 0.35) × 10−11 cm3 molecule−1 s−1. For reaction (2), CF3O radicals are prepared by another source: the thermolysis of the dimer CF3OOCF3 and the derived rate constant is k2 = (4.7 ± 0.9) × 10−11 cm3 molecule−1 s−1. Our results are in reasonable agreement with recent measurements using different techniques.

The rates of the atmospherically important reactions of the CF3O radical with methane (k(6)), ethane (k(7)), and isobutane (k(8)) have been measured at low pressure (approximate to 1 Torr) with the fast flow tube technique associated with a monitoring of the CF3O radical by laser-induced fluorescence; over the following temperature ranges, the respective Arrhenius expressions are as follows: methane (296-573 K), k(6) (4.49 +/- 1.39) x 10(-12) exp(1606 +/- 84)/T cm(3) s(-1); ethane (295-573 K), k(7) = (1.13 +/- 0.34) x 10(-11) exp-(642 +/- 113)/T cm(3) s(-1): isobutane (298-523 K), k(8) = (1.04 +/- 0.2) x 10(-11) exp-(102 +/- 67)/T. A comparison with measurements with other techniques shows that, though our room temperature values of k(6), k(7), and k(8) are in very good agreement with most literature values, our temperature coefficients for k(7) and k(8) are significantly different from the very few other measurements available in the literature. These discrepancies are tentatively ascribed to undetected wall reactions in the highest range of temperatures.