Nitration Of Aromatics And Its Theoretical Study

Nitration is one of the most important organic reactions in industry. It has a wide application in many areas, such as explosive, propellant, chemical intermediates, medicine and pesticide. On the other hand, the mechanism research on aromatic plays an important role in the development of electrophilic substitution theory. Here, we mainly studied the synthesis method of nitro-compounds (mainly nitration), reaction mechanism and pre-evaluating the property of part of these compounds.To solve the more and more serious environmental problem and modify the pollution in industrial production, we discovered several green nitration system:1) Nano metal oxides supported heteropoly acid;2) Acidity ionic liquid/N2O5system;3) surfactant as phase-transfer catalyst;4) various of modified solid acid with high surface. The general research process in each catalytic system was as follow:first part was the characterization of these novel catalysts with different method; secondly, optimize the reaction condition with this catalytic system; finally, investigate the applicability and recycle performance of the catalyst. The results showed that all these catalytic systems could significantly reduce or avoid the using of liquid acid. Besides that, most catalytic systems could change the isomer distribution in nitro-products, the para/ortho ratio of mono-alkylbenzene could be improved to1:1, para/ortho ratio of mono-halogenobenzen would be improved to5:1, part of the disubstituted aromatic could reach9:1. By modifying the selectivity, higher commercial value compounds would be obtained.With quantum chemistry simulation method, the theoretical study mainly focused on two areas:one is the mechanism research of above nitration process with different catalytic system; the other is the evaluation of the property of synthesized or designed nitro-compounds.First, to understanding the nitration mechanism, we attempted to simulate the catalytic process by computer with quantum chemistry software Gaussian. With the simulation result of disubstituted aromatic nitration with surfactant, two main factors that affect the product distribution were found:one was sterical exclusion; the other was charge or spinning electron distribution in benzene ring. Selectivity was the mutual restraint result. Change either factor, the selectivity might be influenced. In the study of nitration of monosubstitute aromatic with solid acid, the sterical exclusion was small enough that we could focus on the other factor. We mainly calculated the interaction between transition metal and aromatic. The results showed that this interaction can modify the distribution of charge or spinning electron and thus leaded to a significant change in selectivity.Next, we studied the preparation and property of2,6-diamino-3,5-dinitropyrdine (LLM-105) and2,6-diamino-3,5-dinitropyrazine-l-oxide. First, the synthetic condition of2,6-diamino-3,5-dinitropyrdine was optimized and got an excellent yield over90%; then, because it was also a potential intermediate for several new and excellent energetic materials, we studied its reduction to2,3,5,6-tetraamineopyridine. In the research of LLM-105, the synthetic method was improved and the yield reached65%. Two different synthetic routes were compared with Gaussian, and the function of each group was discussed in detail. The result showed that π-conjugate of electron cloud involving the whole molecule was the key of its high stability and excellent performance.