Energetics of the reaction pathways for NH2+NO→ products and NH+NO→products

The reaction pathways for NH 2 +NO→products and NH+NO→products have been studied theoretically, using the recently developed quantum chemical method, BAC-MP4 (Bond Additivity Corrections with fourth-order Møller-Plesset perturbation theory), which can provide accurate thermochemical molecular heats of formation and thermodynamic partition functions. In particular, we have calculated the heats of formation ΔH f o and the free energies of formation ΔG f o of the various reactants, products, and intermediates, along with the various activated complexes occurring along the reaction paths. The results indicate that NH 2 +NO forms a stable intermediate which can rearrange to form the products N 2 +H 2 O with no activation barrier. Also, the reaction to form NNH+OH is found to be essentially thermoneutral, making this a potential pathway, particularly at higher temperatures. For NH+NO, we find that the favored products should be H+NNO rather than N 2 +OH, although both can be formed with no activation barrier. Our results are also consistent with the measured activation energy for the reaction of H+NNO →N 2 +OH, which occurs through the same HNNO intermediate.