Research On The Nitration By Dinitrogen Pentoxide

Nitration using N₂O₅ is a new clean technique. The nitrating ability of N₂O₅/organic solvent is mild with high selectivity, while N₂O₅/HNO₃ is stable with strong nitrating ability. So, N₂O₅/organic solvent and N₂O₅/HNO₃ are two complemental nitrating systems.The dissertation is focused on nitration by N₂O₅. The nitration of arene by N₂O₅/CH₂Cl₂ and amine by N₂O₅/HNO₃ were discussed. The main works and results were as follows:(1) The nitration catalyzed by ZSM-5 of arene with N₂O₅/CH₂Cl₂ was studied. Experiments studied the effects of reacting conditions, solvents, catalysts etc on the reaction, and the best nitrating condition was established. Results showed N₂O₅/CH₂Cl₂ was a relatively mild system, its nitrating ability of arene was weak, but the para-selectivity of product was satisfactory. Series of ZSM-5 catalysts could improve para-selectivity of product and meanwhile enhance the yield.(2) The nitration of nitrobenzene with N₂O₅/CH₂Cl₂ catalyzed by HZSM-5 was an acid-catalyzed first-order reaction. Rate constant was in direct proportion to the initial content of nitrobenzene, while had nothing to do with the initial concentration of N2O5. The total reaction could be explained by two steps. The first was a fast pre-equilibrium, the equilibrium position lying well to the right, NO₂⁺ formed by heterolytic cleavage from N₂O₅ transferred to HZSM-5. The second step was slow and rate-determining, catalysis bonded with NO₂⁺ reacted with reactant. The macrodynamics of nitration withnitrobenzene was v = 6561 exp(-11687/RT)c_R.(3) Through quantum chemistry, the geometrical configuration of the transient formation, midbody and product formed by nitration of toluene and chlorobenzene were optimized. The effect of "diffusion control" and the reason of improving the para-selectivity were analyzed in theory.(4) Effects of different kinds of supported heteropolyacids catalysts on the nitration of arene by N₂O₅/CH₂l₂ were studied, and the best catalyst system was confirmed. Through measuring the acid amount, acid strength and BET specific area of supported heteropolyacid, the positive correlation of its acid strength and catalytic activity were discovered, and it was the same with the NO₂⁺ mechanism of traditional liquid-phase nitration, which validated the nitraton of arene by N₂O₅/CH₂Cl₂ an acid-catalyzed reaction with NO₂⁺.(5) HMX was prepared by the nitrolysis of DADN and TPT using N₂O₅/HNO₃ as nitrating agent. According to the original material-methenamine, the yield of HMX were both about 80%, the purity was each 96% and 98%, they were mixtures ofβ-HMX andγ-HMX. This technique showed many advantages: low reaction temperature, mild reaction condition, high yield and purity, which was possible to replace acetic anhydride method to produce HMX.(6) One-step preparation of HMX from DAPT was attempted, using ultrasonic as catalyst and ionic liquid as sorbefacient. Through optimizing the frequency of ultrasonic and other factors, the yield of HMX was enhanced from original 9.6% to 66.8%. Meanwhile, the mechanism of ultrasonic catalysis was also discussed.(7) HNIW was obtained by the nitrolysis of TADNSIW and TAIW using N₂O₅/HNO₃ as nitrating agent. Several effects on the yield, purity and crystalline form of product were analyzed. In the best conditions, the yield of HNIW was 87.2% and 89.2%, the purity was 96% and 99%, they were all mixtures ofα-HNIW andγ-HNIW.