Synthesis And Application Of4-amino-3,5-dinitropyrazole And Its Derivatives

Nitropyrazole compounds have become a hot field of energetic materials in recentyears due to their characteristics of high nitrogen content, high density, high energy, lowsensitivity and environmental friendly.4-amino-3,5-dinitropyrazole(LLM-116) is a highenergy insensitive explosive, owing90%the energy density of HMX, and1.38times theenergy density of TATB. However, the synthesis methods of LLM-116were reported, whichhave many disadvantages, such as complex production processes, low yield and high rawmaterial cost. So it is important to study the synthesis and application of LLM-116.In this paper, two different synthetic routes of LLM-116were optimized, in whichLLM-116were prepared by from4-chloropyrazole and3-nitropyrazole respectively. Theproducts were characterized by IR, MS,1H NMR,13C NMR and HPLC. In the syntheticprocess. The route I in which LLM-116was synthesized starting from4-chloropyrazole bynitration and amination was suitable for industrial production with less steps, higher yieldand less cost. On one hand, the optimum nitration reaction conditions were determined asfollows. Nitration agent was the mixture of nitric acid and sulfuric acid, the ratio ofn(4-chloropyrazole) and n(HNO3) was1:4, the reaction temperature was105℃, and thereaction time was4h. The the purity of4-chloro-3,5-dinitropyrazole recrystallized fromtoluene was up to97%, and the yield was74.2%; On the other hand, amination reaction wasoptimized as follows. NH3·H2O was choose as the amination agent, the ratio ofn(4-chloro-3,5-dinitropyrazole) and n(NH3·H2O) was1:50，the reaction temperature was170℃, and the reaction time was7h. The purity of LLM-116recrystallized from H2O wasup to99%, and the yield was91.2%higher than85%reported by literature. In route II,LLM-116was synthesized starting from3-nitropyrazole by nitration, rearrangement and amination. The optimum nitration reaction conditions of were determined as follows. Thenitration agent was the mixture of nitric acid, acetic anhydride and acetic acid, the ratio ofn(3-nitropyrazole) and n(HNO3) was1:4, the reaction temperature was0℃, and thereaction time was5h. The purity of1,3-dinitropyrazole was up to98%, and the yield was73.4%. In the process of rearrangement, high boiling solvents including benzene nitriles,octyl alcohol and ethylene glycol were used as solvent rearrangement, but it exists someproblems, such as too many by-products and difficulties in purification.TNP was synthesized starting from LLM-116by oxidation. The best oxidation reactionconditions were obtained as follows. The ratio of V(H2SO4) and V(H2O2) was3:2, thereaction temperature was20℃, and the reaction time was2.5h. The purity of TNPrecrystallized from toluene was up to99%, and the yield was47%. The products werecharacterized by IR, MS,1H NMR,13C NMR and HPLC.HMX was coated with a little LLM-116by different solubilities in water. The coatedHMX was a kind of double-deck composite explosive with low impact sensitivity, in whichinside layer was HMX and outsider was LLM-116. The crystal structures of HMX andcomposite explosive were analyzed by VHX. The impact sensitivity results showed that thethe sensitivity of HMX after coating with LLM-116reduced from100%to40%.