Theoretical Design And Precursor Synthesis Of N-heterocyclic Nitramine Compounds

Considering the dangerous sensitivity problem of high energetic explosives, it is urgently required to synthesize novel explosive compounds with low sensitivity to improve the safety of explosives while maintaining their high energetic characteristics. N-heterocyclic nitramine compounds are attributed to high-nitrogen energetic materials, which possess the character of high-nitrogen content and high formation enthalpy, which are the solid compounds of better safety and invariability. The high-energy, high-density, good-stability N-heterocyclic nitramine compounds which contain carbon, oxygen, hydrogen, nitrogen have been always exploring in the industry, military affairs, spatial application, etc. So it is important to study the synthesis and properties of N-heterocyclic nitramine compounds for the theoretical study and military application.The insensitive property of N-heterocyclic explosives is combined with the high energy of nitramine explosives, and the concept of N-heterocyclic nitramine explosive is proposed, into which the nitramine group with N-N bonds is introduced as much as possible. Based on the research of regular relationship between molecular as well as crystal structure and explosive property as well as security performance, the dissertation is devoted to systematic researches on the structures and series of N-heterocyclic nitramine compounds, using modem theoretical and computational chemistry methods, such as density functional theory (DFT) and molecular mechanics (MM). The synthetic routes are designed and the precursors are obtained with condensation. The specific research contents include the following aspects: Investigation on the structures and properties of N-heterocyclic nitramine compounds:The fully optimized structures of pyridineheterocyclic energetic derivatives, imidazole/pyrazole-based pyridine derivatives and benzeneheterocyclic energetic derivatives were obtained at the density functional theory DFT-B3LYP level. Force field method was adopted to predict the crystal structures of pyridineheterocyclic energetic derivatives, imidazole/pyrazole-based pyridine derivatives and benzeneheterocyclic energetic derivatives. According to the volume inside a contour of0.001e·Bohr-3, the molecular theoretical density was evaluated, and detonation velocity (D) and detonation pressure (P) were estimated according to the Kamlet-Jacobs equation. Bond dissociation energies (BDEs) of three possible trigger bonds in their thermolysis were computed, and their pyrolysis mechanisms were ascertained to be the homolysis of N-NO2bond.Based on DFT-B3LYP/6-31G(d), the fully optimized structures, assigned infrared (IR) spectra, and thermodynamic properties (C°p,m、S°m禾H°m) related with the temperature in200K-800K of Cage-HMX and Cage-bi-HMX were obtained. Force field method was adopted to predict the crystal structures of Cage-HMX and Cage-bi-HMX. The heats of formation (HOFs) of Cage-HMX and Cage-bi-HMX were calculated with the help of the reaction of formation. The explosion heat (Q), detonation velocity (D), and detonation pressure (P) were calculated using Kamlet-Jacobs equations. The bond dissociation energy was estimated. According to the quantitative standard of energetics and stability as a high-energy-density compound, Cage-HMX and Cage-bi-HMX essentially satisfies this requirement.Molecular mechanics method was adopted to predict the crystal structures of monocyclic nitramines, bicyclic nitramines and tricyclic nitramines. DFT was used to study theoretical density (p) and HOF. The Q, D, and P were calculated using Kamlet-Jacobs equations. The bond dissociation energy and energy gap (△E) were estimated. Several compounds with excellent detonation properties were found. The effects of substituents on p, HOF, Q, D, and P were studied. With the increasing number of substituents, all of them increase. Study on the precursor synthesis of N-heterocyclic nitramine compounds:Two N-heterocyclic nitramine precursor,1,5-2H-diimidazo[b, e]pyridine and2,9-dialdehyde-5,13-dithio-2,4,6,7,9,11,12,14-octaaza-tricyclo[8.4.0.03,8]tetradecane, were prepared by condensation reaction. The reaction mechanism and the effects of reaction medium, pH and other factors on the reactions were investigated.