Ab initio study of protonated nitrosamide: a possible intermediate in the deNO x process

Ab initio calculations on protonated nitrosamide, a possible intermediate in the deNO x process, have been performed. A mechanism involving the formation of an intermediate NH3NO+ was proposed by Egsgaard, Carlsen and Madsen and tested by performing flame experiments with mass spectrometry. In the present work, the absence of NH3NO+ in the flame has been supported on the basis of its structure. This cation is observed to be a loosely bound adduct of NH3 and NO+ at and beyond the HF level of theory. On the other hand, NH2NOH+ is found to be a covalently bonded compound at all theoretical levels. Topographical analysis of electron density and electrostatic potential has been utilized to gain insight into bonding properties and to predict the possible sites of protonation. The vibrational spectra of both protonated nitrosamide cations are reported. The feasibility of proton transfer reactions of NH3NO+ with ammonia and water are investigated using heats of reactions. These values indicate that such a reaction is possible with NH3 but unfavorable with H2O.