- Kinetics and Thermochemistry of the Reaction CCl3 + NO + M CCl3NO + M
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The kinetics and equilibrium constant of reaction 1, CCl3 + NO + M CCl3NO + M, were investigated using pulsed-laser photolysis/time-resolved mass spectrometry at low pressure, 0.5-12 Torr, and flash-photolysis/UV absorption spectrometry at high pressure, 110-760 Torr.These pressure ranges cover most of the fall-off region.Fall-off curves were measured at 263, 298, and 373 K and a determination of the rate constant was performed at 465 K, 760 Torr.RRKM calculations were performed for accurate extrapolation to the low and high pressure limits.The rate expressions obtained are, using the formalism of Troe, k1(0) = -29>(T/298 K)(-5.5+/-0.2) cm6 molecule-2 s-1 and k1(infinite) = -12>(T/298 K)(-1.0+/-0.3) cm3 molecule-1 s-1, with Fc = 0.66 exp(-T/600 K).The collisional efficiency factor βc = (0.43 +/- 0.04)(T/298)(-1.0+/-0.2) is reasonable, thereby establishing the consistency between kinetic and thermochemical data.The rate expression at 760 Torr is k1(760 Torr) = -12>(T/298)(-2.65+/-0.2) cm3 molecule-1 s-1.The equilibrium constant was measured at 480 and 486 K and the entropy of reaction was calculated using statistical thermodynamics, with the purpose of determining the enthalpy of reaction: ΔH0298 = -125 +/- 8.5 kJ mol-1.This value, corresponding to the bond dissociation energy D(CCl3-NO), is significantly smaller than the corresponding bond dissociation energies in CH3NO and in CF3NO: 172 and 167 kJ mol-1, respectively.Ab initio calculations of the above bond dissociation energies have yielded values in good agreement with experimental data.
- Masanet, J.,Caralp, F.,Jemi-Alade, A. A.,Lightfood, P. D.,Lesclaux, R.,Rayez, M. T.
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- Gas-Phase Ion-Molecule Reactions of the Nitric Oxide Anion
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The chemical reactivity of nitric oxide anion (NO(1-)) with a variety of organic neutrals at ambient energies and in argon bath gas has been probed using the flowing afterglow technique.The reactions fall into four main classes: electron transfer, dissociative electron transfer and/or displacement, collisional detachment, and clustering.Electron transfer can occur when the neutral reactant possesses a positive electron affinity greater than the electron affinity of NO., but does not always do so.Bimolecular substitution at sulfur is shown to occur with dimethyldisulfide, but for other substrates, distinguishing between displacement and dissociative electron transfer is not possible.Collisional detachment is the exclusive reaction channel observed for a few of the molecules examined and occurs to some extent with many of the neutrals tested.Cluster ion formation between NO(1-) and a number of the reactant neutrals which possess permanent dipole moments is observed.Additional pathways were observed for several of the neutrals examined.The collected observations are discussed in light of the general theory of ion-molecule reactions.
- Rinden, Elizabeth,Maricq, M. Matti,Grabowski, Joseph J.
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p. 1203 - 1210
(2007/10/02)
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