Computational Chemistry, Nitramide, Intermolecular Hydrogen Bond Nitramide was investigated by multinuclear NMR spectroscopy, X-ray-diffraction and computational methods. The crystal structure analysis at various temperatures reveals a planar conformation of the molecule with a N-N bond length corresponding to a bond order between one and two. Hydrogen bonds connect the nitramide molecules side-on and end-on. This leads to the formation of layers in the crystal. Calculations were performed to explain the shorter N-N bond length in the crystal compared to the gas phase. The nitramide trimer is used as a model.

The structures of α‐ and β‐HMX were fully optimized and the vibrational frequencies computed at the hybrid DFT B3LYP/6‐31G(d, p) level of theory. The DCI+mass spectrum of HMX using ammonia (NH3) as a “soft” ionising gas is reported. Field desorption mass spectrometry (FD) was used because of the high molecular intensities and low fragmentation. The FD spectrum shows only one significant peak at m/e 297 due to the protonated molecular ion [M+H]+. These observations clearly establish that under the conditions of CI and FD mass spectrometry experiments HMX is present in the gas phase (without decomposition) prior to the chemical ionisation.

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