Kinetics and Thermochemistry of the Reaction CCl3 + NO + M CCl3NO + M

Article abstract of DOI:10.1021/j100115a027

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) = <(1.4 +/- 0.3)*10^-29>(T/298 K)^(-5.5+/-0.2) cm⁶ molecule^-2 s^-1 and k₁(infinite) = <(7.5 +/- 1.5)*10^-12>(T/298 K)^(-1.0+/-0.3) cm³ molecule^-1 s^-1, with F_c = 0.66 exp(-T/600 K).The collisional efficiency factor β_c = (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) = <(5.2 +/- 1.0)*10^-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.