We have undertaken a comprehensive study of the reaction NH2(X2B1) + NO → N2 + H2O (1a) and NH2(X 2B1) + NO → N2H + OH → N2 + H + OH (1b). Experimental measurements of the reaction rate coefficient and product branching fraction are combined with accurate ab initio calculations to give a detailed picture of this important reaction. The rate constant of reaction 1 was investigated in the temperature range 203 K ≤ T ≤ 813 K using the laser photolysis/CW laser-induced fluorescence technique for production and detection of NH2. The rate coefficient was found to be pressure independent between 10 and 100 Torr and is well described by k 1(T) = 1.65 × 10-7 T -1.54 exp (−93 K/T) cm3/(molecule·s). The deuterium kinetic isotope effect for the reactions of NH2 and ND2 with NO was investigated at temperatures between 210 and 481 K. A small, temperature-independent isotope effect of k H/k D = 1.05 ± 0.03 was found. Additional experimental work focused on measuring the product branching fraction for production of OH, Φ1b, and its deuterium isotope effect at room temperature. Measurements were performed using the discharge-flow technique with mass spectrometric detection of products. OH from channel 1b was reacted with excess CO and measured as CO2. The room temperature branching fraction was measured as Φ1b = 9.0 ± 2.5% (NH2 + NO; T = 298 K) and Φ1b = 5.5 ± 0.7% (ND2 + NO; T = 298 K). Theoretical calculations have characterized the stationary points on the potential energy surface connecting reactants with products using G2 and G2Q levels of theory. These calculations support the experimentally observed temperature dependences and kinetic isotope effects.

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Absolute rate constants were obtained for CN radical reactions with HCN and C2N2 employing the method of laser photolysis/laser induced fluorescence. The rate constants were found to be temperature dependent in the range 300–740 K and pressure independent in the range 100–600 Torr. The rates for CN+HCN may be described well, in units of cm3/s, by k(HCN)=2.50×10−17T1.71 exp(−770/T), which includes the shock tube results of Szekely et al. at 3000 K [Int. J. Chem. Kinetics 15, 1237 (1983)]. The measured rates for CN+C2N2 may be described well by k(C2N2)=2.19×10−21T2.70 exp(−325/T). Rice–Ramsperger–Kassel–Marcus (RRKM) theory calculations employing transition state parameters predicted by the BAC-MP4 method were able to account for the effects of temperature and pressure on both reactions.

Absolute rate constants were measured for the reaction CN + CH20 over the temperature range 297-673 K and CN + 1,3,5-trioxane over the range of 297-600 K by the laser photolysis/laser induced fluorescence technique. The rate constants for these reactions can be effectively represented, in units of cm3/s, by: W(CH20) = 2.82 X p.72 exp(718/T), and k(l,3,5-trioxane) = 1.39 X T'.26 exp(1333/T), respectively. Transition state theory calculations were able to fit the temperature dependence of the CN + CH20 rates relatively well. We attempted to correlate the CN reaction rate with CH20 and other molecules which occur through simple abstraction with the corresponding OH reaction rates, yielding only a qualitative linear correlation for a majority of the processes. The reactions which deviated significantly from linearity include those which contain strong dipoles, highlighting the significant role long-range attractive forces play in CN and OH reactions. Using a simple electrostatic potential, cross-sections were determined for reactions with CN. No linear correlation was found between the calculated and experimental cross sections for the majority of the reactions studied. 0 1993 John Wiley & Sons, Inc.