Theoretical Study Of Stabilities And Tautomerism On Energetic Material N_nH_n(n=4～6)

The stabilities and tautomerisms on energetic material NnHn (n=4⁶) have been studied by Gaussian98 program. The contents which are studied in this thesis are as follows:1. Theoretical study of stabilities and tautomerism on energetic material N₄H₄.2. Theoretical study of stabilities and tautomerism on energetic material N₅H₅.3. Theoretical study of stabilities on energetic material N₆H₆.Possible isomers and their tautomerisms on energetic material NnHn(n=4⁶) are optimized by density functional theory (DFT).The calculations are performed by B3LYP/6-311++G(d,p) basis set. The reality of the isomers and transition states in each system are proved by the results of vibration analysis. And the densities of bond critical points (BCP) are calculated using AIM2000 program. Furthermore, G3B3 method is employed to obtain more accurate energies basing on optimized geometries. Because hydronitrogen compounds usually have high energy, heat of formation (HOF) of various isomers in NnHn(n=4⁶) are also calculated respectively. Nowadays practical conditions limit the experimental researches of hydronitrogen compounds, so the theoretical studies play a vital part in the field of research, which are mainly focused on ringy conformations. We try to explain the stabilization and tautomerism of isomers on NnHn(n=4⁶) through the analysis of conformation, stability and tautomerism. Our study showed that these compounds may be a kind of potential energetic material, and our work provides some useful information for further experimental study of them. Eleven isomers of N₄H₄, twenty-three isomers of N₅H₅, and sixty isomers of N₆H₆ have been found in the thesis. The results of studies indicate that, the three systems have the same characteristics, the compounds of N=N double bonds are beneficial to their stability; the energies and the heat of formation(HOF)of ringy isomers are higher than chain isomers, which indicate that the ringy isomers are of more potential energetic material. In addition, all the four-membered cyclotetrazanes isomers are of the highest energies and heat of formation in each system, so their stabilities are the lowest. Along with the numbers of nitrogen atom increasing, the heats of formation in every system are also increasing. Their barrier energies of tautomery reactions are different, so their tautomerisms are also different.