Studies On The Syntheses And Properties Of Novel High-Nitrogen Triazole Energetic Compounds

As an important part of novel energetic materials,high-nitrogen energetic compounds have attracted the great attention of researchers for their high heat of formation,high density and environmental-friendly detonation products.There are abundant energeitc C N bonds in the molecular structure of high-nitrogen energetic compounds based on triazoles,which are different from the classic energetic materials.These energetic bonds are the main source of chemical potential energy for energetic compounds.In addition,the stability of energetic materials could be effectively improved by constructing the coupled or fused triazole backbones.Then,the introduction of diffenert explosive groups would further improve the detonation properties of energetic compounds.In this dissertation,several series of energetic compounds based on triazoles were studied by designing planar energetic frameworks,introducing nitro,nitroamino and gem-dinitromethyl groups,synthesizing energetic ionic salts and constructing the metal-organic crystal configuration.It could be mainly divided into the following three parts.1.Studies on the syntheses and properties of bis（gem-dinitromethyl）substituted triazole and bis（chlorodinitromethyl）substituted energetic compounds.4,5-Dicyano-1,2,3-triazole was chosen as the raw material and synthesized from diaminomalenitrile by diazotization.Then,the addition and chlorination reactions were carried on it to yield 4,5-bis（carboxoxim dichloride）-1,2,3-triazole as nitrification substrate.It was nitrated by a new nitrification solution of mixed trifluoroacetic acid,trifluoroacetic anhydride and 100%nitric acid.Afterwards,the nitrification products were further treated with the methanol solution of potassium iodide to yield metal-organic energetic compound153 with 3D"cage-like"crystal parking system.Besides,the nitrification products under different reaction conditions were also analyzed and isolated.The structure,density and stability of all these newly synthesized energetic compounds were characterized.Furthermore,the detonation properties of these compounds were studied theoretically.Among them,the detonation velocity of potassium salt 153 is 8715 m s^-1,which is close to that of the classical explosive RDX(D=8795 m s^-1).Its main decomposition product is nitrogen（48.1%）.The potassium salt 153 has high energy density(2.04 g cm^-3)and high mechanical sensitivity,which indicate its potential to become a lead-free primary explosive.A series of bis（chlorodinitromethyl）substituted energetic compounds were chosen to study the nitration of carboxoxim-dichloride.The nitration product was isolated and purified.As a result,the single crystal of compound 154 was obtained and its specific structure was characterized by X-ray single crystal diffraction.In addition,the density and thermal stability of compound 154 were studied.Its theoretical detonation properties were also studied.The detonation velocity of compound 154 is 8400 m s^-1,which is close to that of structurally similar compound 4,4’-bis（fuorodinitromethyl）-3,3’-azofurazan（BFNAF）(8492 m s^-1).But theΔ_fH of 154 is much higher than that of BFNAF(154:816.5 k J mol^-1,BFNAF:175.8 k J mol^-1).2.Studies on the syntheses and properties of energetic compounds based on1,2,3-triazole coupled with 1,2,4-triazole framework.4,5-Dicarboxy-1,2,3-triazole was obtained by the oxidation of benzotriazole under the alkaline condition of potassium permanganate.Then,4,5-dicarboxy-1,2,3-triazole cyclized with diaminoguanidine hydrochloride to construct the 4,5-bis（1,2,4-triazolyl）-1,2,3-triazole energetic framework.The high-nitrogen energetic ionic salts（156-166）were further synthesized based on the tricyclic nitrogen-rich compound 155.The structural characterizations,thermal stabilities and sensitivities of all these newly synthesized compounds were studied.Besides,the crystal structures of several compounds were analyzed by X-ray single crystal diffraction.It is worth noting that compound 161 was proved to be a very rare zwitterionic energetic salt.Compounds 158 and 161 have good detonation properties.Their detonation velocities are 8770 m s^-1 and 8545 m s^-1,which are close to the traditional explosive RDX(D=8795 m s^-1).Furthermore,the intermolecular and intramolecular hydrogen bond interactions were analyzed by a series of quantum chemical methods.The structure-property relationships of the compounds were studied.In addition,compounds 158and 161 with high gas-producting capacity were chosen for constant-volume combustion experiments.The results show that compounds 158 and 161 have higher gas-producting pressure(158:P_max=10.83 MPa;161:P_max=13.58 MPa)and faster pressure-rising rate(158:[d P/dt]_max=163.8 GPa s^-1;161:[d P/dt]_max=174.4 GPa s^-1),which are much better than the traditional gas generant guanidine nitrate(GN,P_max=4.20 MPa;[d P/dt]_max=79.2 GPa s^-1).It means that compounds 158 and 161 have the potential to be used as components of gas generant.Another planar tricyclic triazole structure was redesigned based on4,5-dicarboxy-1,2,3-triazole.The derivative 167 was obtained by esterification and cyclization of 4,5-dicarboxy-1,2,3-triazole.In order to further improve the detonation performance,the nitro and nitramine groups were introduced into the planar backbone by the diazotized oxidation and nitration,respectively.As a result,nitration product 168 and nitramination product 169 were obtained.The planar structure of compound 168 was proved by X-ray single crystal diffraction.Additionally,a series of energetic ionic salts 170-180 were prepared by Br?nsted acid-base reaction.Their structures,thermal stabilities and sensitivities were fully characterized.The detonation properties of compounds 173 and 180 are close to that of RDX(173:D=8720 m s^-1,180:D=8748 m s^-1,RDX:D=8795 m s^-1).Besides,their impact sensitivity（IS）and friction sensitivity（FS）（173:IS=35 J,FS=360 N;180:IS=40 J,FS=360 N）are better than TNT.In order to get better understanding of the relationships between structure and properties,several quantum chemical analyses were carried.It shows that these newly synthesized energetic compounds with planar molecular structure have good stability,high energetic properties and low sensitivity.Besides,compounds 173 and 180 were tested by constant-volume combustion experiments.The results(173:P_max=16.20 MPa;180:P_max=11.21 MPa)show that these two energetic compounds have the potential to be used as components of green gas generant.3.Studies on the syntheses and properties of multi-site cationic energetic compounds based on monocyclic/fused hetercyclic 1,2.4-triazole ringsGlycine,a cheap and easily available industrial raw material,was used as the reaction substrate.Compound 181 was obtained by one-step cyclization.Then,a series of monocyclic compounds 182-188 were synthesized via Br?nsted acid-base reaction as divalent cationic energetic salts.Inspired by this multi-cationic structure,the substrate A with three cationic sites was designed and synthesized.Subsequently,the crystal structure of compound 197 was confirmed by X-ray single crystal diffraction analysis and indirectly proved the structure of intermediate B.Although the substrate A was not obtained as expected,fused-cyclic compound 189 could also be synthesized through the cyclization of intermediate B with cyanogen bromide under acidic condition.A series of fused-cyclic energetic salts 190-196with dicationic sites were subsequently synthesized based on compound 189.The structures,thermal stabilities and sensitivities of all these newly synthesized energetic compounds were fully characterized.Besides,the specific molecular structures of compounds 182,183,185and 193 were confirmed by X-ray crystal analysis.Furthermore,the detonation velocity of5-nitraminetetrazole salt 190(D=8843 m s^-1)is higher than RDX(D=8795 m s^-1)and its corresponding monocyclic energetic compound 182(D=8748 m s^-1).In addition,the mechanical sensitivities of fused-cyclic energetic compounds are generally better than that of corresponding monocyclic ones.By means of quantum chemical analysis,such as Hirshfeld surface analysis and NCI analysis,the difference of structure and properties between corresponding monocyclic/fused-cyclic energetic compounds were further studied.It demonstrates that the construction of fused-cyclic structure is an effective method to search energetic compound with high energy and low sensitivity.Moreover,the results of constant-volume combustion experiments(182:P_max=10.18 MPa;190:P_max=9.16 MPa)show that compounds 182 and 190 are also potential gas generant components.