One-pot synthesis, thermal analysis, and density functional theory study of methyl urotropine perchlorate

An energetic material methyl urotropine perchlorate (MUTP) was synthesized from urotropine, perchloric acid, and triethylenediamine. The single crystal structure of the energetic salt was characterized by X-ray single crystal diffractometer. The results show that the single crystal of MUTP is an orthogonal crystal system with Pnma space group. The thermal decomposition process of MUTP was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) technology. There were two exothermic peaks in TGA and DSC test, and the peak temperatures (T_p) were 261.61°C and 366.75°C, respectively. The thermal stability of MUTP was up to 247.10°C. Geometric optimization, frontier molecular orbitals, electrostatic potential (ESP), and weak interaction were explored by density functional theory using Gaussian 16. It is found that MUTP has a large energy gap (5.94 eV), which is larger than that of HMX (5.84 eV). The results of reduced density gradient method show that there are dense hydrogen bond interactions in MUTP with high electron density and intensity. In addition, a strong spatial repulsion is formed at the center of the cage.