Energetic, structural, and kinetic characterization of the hydrogen abstraction reaction N(4S) + CH4 → NH(X3Σ−) + CH3

Geometries, frequencies, energies, and rate constants of the reaction N(4S) + CH4 → NH + CH3 were computed using coupled-cluster theory, correlation-consistent basis sets, and extrapolations schemes to assess the complete basis set limit energies. Our best calculation gives a classical barrier height and reaction energy of 32.9 and 29.3 kcal/mol, respectively, and 24.6 kcal/mol for the reaction enthalpy (ΔH00). Thermal (200-2000 K) rate constants were calculated with the canonical variational transition state theory, and indicate a very slow reaction when compared with the ones with N(2D) and N(2P). Using the CVT/μOMT method, the value of H/D KIE is 6.3 (300 K).

Graphical abstractGeometries, frequencies, energies, and rate constants of the reaction N(4S) + CH4 → NH + CH3 hydrogen abstraction were computed using coupled-cluster theory and two hierarchical series of basis sets of Dunning. Three schemes of energy extrapolations were used to assess the complete basis set limit (CBS) energies.Download full-size image