ABSOLUTE RATE-CONSTANT MEASUREMENTS OF CF(X-PI-2 REACTIONS .2. REACTIONS WITH O, N, NO2, N-2, N2O, F, AND C3H4

Rate coefficients of the elementary reactions of CF(X (2) Pi, upsilon = 0) with O, N, and NO2 at T = 294 K and pressures in the range of 2-10 Torr have been determined, using laser photodissociation/laser-induced fluorescence (LPD/LIF) techniques. The CF(X (2) Pi) radicals were generated by excimer laser photolysis of CF2Br2 at 248 nm. Real-time exponential decays of CF(X, upsilon = 0) were monitored by LIF (A (2) Sigma(+), upsilon' = 1 <-- X (2) Pi, upsilon' = 0 transition) at varying concentrations of the reactant, in very large excess over CF. Atomic reactants were produced from the corresponding elemental gases in a microwave discharge. The rate constants for the title relations were found to be k(O) = (3.9 +/- 0.8) x 10(-11) at p = 5 and 10 Torr, k(N) = (3.9 +/- 0.8) x 10(-11) at p = 2 and 10 Torr, and k(NO2) = (4.0 +/- 0.8) x 10(-11) cm(3) molecule(-1) s(-1) at p = 2 and 10 Torr (He or Ar as bath gas). Besides, an upper limit of k less than or equal to 10(-14) for p less than or equal to 10 Torr was established for the reactions of CF(X) with N-2, N2O, and C3H4, and of k less than or equal to 10(-13) for CF + F. The present results, together with earlier data for other CF reactions, are compared with available literature data for analogous reactions of CH. It is argued that CF generally reacts more like a doublet radical and shows only little of the carbyne reactivity typified by CH; the principal reason is that the ''vacant'' carbon orbital of CF is partially filled by fluorine 2p pi back-donation.