Quantum Chemical Study On Structure And Properties Of Heterocyclic Aromatic Energetic Compound

High-nitrogen heterocyclic compounds have high Positive enthalpy of formation, largedensities, low sensitivities and are easy to reach oxygen balance, Which their high nitrogenand low carbon and hydrogen contents in molecular stucrurtes. All these features meet therequirements of high-energy insensitive explosive. Owing to time-consuming, expensive anddangerous, and many unpredictable effect factors in the tests of explosives, theoretical studieson the relations between structures and properties of triazoles and pyrazines play a necessaryand important role in investigating and designing high-energy insensitive explosive.In this dissertation, we studied 1,2,3-triazole, 1,2,4-triazole and 19 nitrotriazolederivatives systematically by using the density functional theory （DFT） B3YLP/631+G^**method, and the statistical thermodynamics theory was used to calculated their geometries,electronic structures and thermodynamics data . We studied and found the substitutent effectof nitro derivatives of triazoles and the relationship between the structures and properties oftriazole compounds. It is found that C–N and N–N bond are the weakest bond, referred to asthe“trigger linkage”in the process of detonation for 1,2,3-triazole, Instead of homolysis ofC=C frame bond. N–N bond are the weakest bond and the most easily broken in the ring of1,2,4-triazole. And the results are correspond to the experimental facts.In order to calculate standard enthalpies of formation （△（H_f^θ,298K）） for nitrotriazolederivatives, we use B3LYP/6-31+G^** and B3P86/6-31+G** two different levels anddesigned isodesmic reactions corresponding to 19 title compounds. The coherency obtainedfrom the two B3P86/6-31+G^** and B3LYP/6-31+G^** calculation levels demonstratesprecision and suggests reasonable accuracy. The calculation results show that the HOFs ofnitrotriazole decline when methyl is introducted on triazole ring, and When the number ofmethyl group substituted on the triazole ring is equivalent, the more the number of NO₂groups are, the more the HOFs of title compounds are. The various trend between bonddissociation energies and heat of formation are consistent and these indicate our calculation are reliable.7 picrylaminotriazole （PATO） homologues and 14 polynitropyrazine-N-Oxidesderivatives were systematically studied by the B3LYP/6-31+G** method. It gave structures,energies and thermodynamic function. Compared the theoretical with experimental results,and the relationship between the structures and properties of picrylaminotriazole （PATO）homologues and polynitropyrazine-N-Oxides derivatives was found out.Based on statistical thermodynamics, The heat capacity, entropy and enthalpy of somerepresentative compounds at different temperatures ranging from 100～1200 K were obtainedby statistic thermodynamics. The title compounds molar volume and theoretical density wereestimated using the Monte-Carlo method based on 0.001 e bohr_-3density space. Furthermore,the detonation velocity and pressure of the derivatives were estimated by the Kamlet-Jacbosequation. All about These set up a quantitative basis for the HEDM desing.The homolytic bond dissociation energies （BDEs） corresponding to–NO2 group removalfrom carbon site on imidazole and pyrazine ring were calculated at UB3P86/6-31+G^** level,and the weakest bond has been determined. Further, the correlation is developed betweenimpact sensitivity h50and the ratio （BDE/E₀） of the weakest bond BDE to the total energy E0.and we extrapolate this relationship to predict the impact sensitivities for compounds whereexperiments are not available. It is found that most of the title compounds are insensitivetowards impact stimuli with their h50larger than 60.0 cm.In summary, this work gave a lot of basic research data for triazole and pyrazineheterocyclic compounds, and some valuable rules was also summed up, which played atheoretical reference role in applications and experimental synthesis of these kinds ofheterocycle energetic materials.