A Combined Experimental and Theoretical Study of HMX (Octogen, Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine) in the Gas Phase

Abstract

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.

The pressure-induced phase transition of the solid β–HMX

“…A large amplitude oscillation was observed only in the nitrogen-nitrogen bond, which indicated the importance of compressed N-N bonds in the crystal for bringing about the initial decomposition process of nitramines [10]. The vibrational spectra of single molecule HMX have been studied using quantum mechanical methods [11,12]. However, to the best of our knowledge, the vibrational properties of HMX crystal have not been explored theoretically.…”

High-Resolution Field Desorption/Ionization Fourier Transform Ion Cyclotron Resonance Mass Analysis of Nonpolar Molecules

“…Many thermally labile, nonvolatile, and high molecular weight molecules can be ionized by FD, yielding clean mass spectra of intact molecular ions. − FI and FD gained prominence in the late 1970s and early 1980s. They were applied to a wide variety of analyses, including explosives, hydrocarbons, polymers, , carotenoids, inorganic complexes, textiles, and phospholipids . FI is well-suited to complex mixture analysis because it generates true molecular ions, M + • , by electron tunneling, rather than quasimolecular ions resulting from adduction of a proton or other ion.…”