Studies On The Synthesis And Properties Of High-performance Insensitive Aza-bicyclic Energetic Materials

Nitrogen-rich heterocycles are one of the most important structural motifs in the design of high energy density materials(HEDMs).High nitrogen content energetic materials were found to be preferable to traditional eneregtic materials,the presence of large number of energetic C-N,C=N,N-O and N=N bonds in these heterocycles supports high performance because of high positive heats of formation and high densities.However,there is an essential contradiction between the energy and safety of explosives,the higher the energy and the worse the security.In this paper,a new type of aza-bicyclic and an ester based backbones are designed by optimizing the molecular structure.Series of high-performance insensitive compounds were synthesized,and their properties have been investigated.It mainly consists of the following four parts:1.Studies on the synthesis and properties of polynitro compounds based on esteryl backbonesOxalic acid,or polynitrobenzoic acid were dissolved in 2,2,2-trinitroethylsulfuric acid prepared from 2,2,2-trinitroethanol and chlorosulfonic acid,which led to the formation of polynitro esters.Among them,bis(2,2,2-trinitroethyl)oxalate(138)possess good performance(D=8718m s-1,P=34.7 GPa),which are comparable to that of RDX(D=8795m s-1,P 34.9 GPa),The oxygen balance and oxygen percent of 138 are 7.69%and 61.52%,respectively.Moreover,138 exhibit moderate sensitivity,indicate 138 possess the potential to become a high-energy oxidant.2.Studies on the synthesis and properties of energetic compounds based on 4-(1,2,4-triazol-3-yl)furazanAn analogue-oriented synthetic route for the formulation of 5-nitroimino-1,2,4-triazoles has been explored by Coupled-Annulation reaction using hydrazide with 1-methyl-1-nitroso-2-nitroguanidine,which led the formation of compounds 143-146.3-nitro-4-(5-nitramino-1,2,4-triazol-3-yl)furazan(147)and 3-nitramino-4-(5-nitramino-1,2,4-triazol-3-yl)furazan(148)were prepared with 3-amino-4-(5-nitramino-1,2,4-triazol-3-yl)furazan(143)by oxidation,nitration.Among them,148 possess good performance(Z=9258 m s-1,P=39.0 GPa),which are better than that of HMX(D=9144m s-1,P=39.2 GPa).Remarkably,the IS value of 148(18 J)is higher than that of TNT(15 J),the reason for the low sensitivities of the neutral compounds in the series is explained reasonably by quantum calculations.Additionally,a new family of energetic salts based on compounds 147 and 148 were synthesized.The formulation of 5-amino-1,2.4-triazoles has been explored by Coupled-Annulation reaction using ester with bis(1-aminoguanidinium)sulphate,which led the formation of 3-amino-4-(5-amino-1.2,4-triazol-3-yl)furazan(149).3-nitramino-4-(5-nitramino-1,2,4-triazol-3-yl)furazan(148),3-nitro-4-(5-nitro-1,2,4-triazol-3-yl)furazan(150),N,N-bis(trinitroethyl)-3,5'-diamino-4-(1,2.4-triazol-3-yl)furazan(151),N,N'-bis(trinitroethyl)-3,5'-dinitramino-4-(1,2,4-triazol-3-yl)furazan(152)were obtained by nitration,oxidation,Mannich reaction with 2,2,2-trinitroethylanol and further nitration of compound 149.150 has the excellent detonation performance(D=9152 m s-1,P=37.1 GPa)than that of HMX,and more insensitivity towards mechanical stimulus(23 J)than TNT,indicate 150 possess the potential to be a new type of high-performance insensitive energetic compound.3.Studies on the synthesis and properties of energetic compounds based on 4-nitro-5-(1,2,4-triazol-3-yl)-1,2,3-2H-triazoleMethyl 4-nitro-1,2,3-2H-triazole-5-carboxylate was readily converted with bis(1-aminoguanidinium)sulphate to form 4-nitro-5-(5-amino-1,2,4-triazol-3-yl)-1,2,3-2H-triazole(171).For the first time,the bicyclic structure 4-(1,2,4-triazol-3-yl)-1,2,3-2H-triazole was constructed.Based on the amino group in compound 171,nitramino,nitro and azo groups were prepared by nitration,oxidation and oxidative coupling to prepare the corresponding compounds.Consequently,a series of 4-(1,2,4-triazol-3-yl)-1,2,3-2H-triazole-based nitrogen-rich salts were obtained.The detonation velocity and IS value of salt dihydrazium 4-nitro-5-(5-nitroimino-1,2,4-triazol-3-yl)-1,2,3-2H-triazolate(185)are 9341 m s-1 and 28 J,respectively.Additionally,185 can be ignited by PbN3,which indicate that 185 is the ideal High-performance Insensitive Energetic Materials.4.Studies on the synthesis and properties of energetic compounds based on furoxan3-Methyl-4-formylfuroxan was synthesized using(E)-2-Butenal as starting material.For the first time,2,4,6-trinitrophenyl structure,trinitro ester group and 5-nitramine-1,2,4-triazole structure were introduced into the furoxan ring to prepare 4-methyl-1,2,5-oxadiazole-3-carboxaldehyde 5-oxide(2,4,6-trinitrophenyl)hydrazine(196),2,2,2-trinitroethyl 4-methyl-1,2,5-oxadiazole-3-carboxylate 5-oxide(197)and 3-methyl-4-(5-nitramino-1,2,4-triazol-3-yl)furoxan(198).The thermal behaviours and explosive properties of resulting energetic derivatives were also investigated by experimental and theoretical methods.