Studies On The Synthesis And Properties Of High Nitrogen Energetic Compounds Based On Heterocyclic Rings Containing Nitrogen And Oxygen

To synthesize high energy density materials(HEDMs)with energetic properties better than octagon(HMX),while making them greener and safer for environmental and personal safety,researchers across the globe have synthesized many high HEDMs with various potential applications.It has been observed that nitrogen rich energetic compounds with poly nitro moieties along with minimum hydrogen content are most helpful in improving the density of CHON explosives.Unlike traditional explosives,which derive most of their power from the oxidation of carbon backbone,modern HEDMs are based on nitrogen rich heterocyclic rings containing nitrogen and oxygen heteroatoms.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 density.Additionally,the presence of polynitro moieties in energetic compounds can further improve their density and oxygen balance.Therefore,introduction of polynitro groups/moieties on the heterocyclic rings containing nitrogen and oxygen atoms is one of the most promising approach to design novel structures with excellent detonation performance.The thesis entitled"Studies on the Synthesis and Properties of High Nitrogen Energetic Compounds based on Heterocyclic Rings Containing Nitrogen and Oxygen" presents the results obtained from the research work carried out on the synthesis,characterization and exploration of the chemistry of series of high nitrogen energetic compounds with novel structures.The work carried out has been broadly divided into five parts.1.The studies of synthesis and properties on the energetic compounds based on nitroform group and the azo or azoxy bridged bis(furazan)3,3-Diamino-4,4’-azofurazan(DAAF)was synthesized by using the oxidant,NaClO,starting from 3,4-diaminofurazan(DAF).3,3-Diamino-4,4 azoxyfurazan(DAOAF)can be obtained by using OXONETM as a stronger oxidant compared with NaCIO,starting from DAF.To study the reaction of 2,2,2-trinitroethanol(TNE)with DAAF or DAOAF using Mannich reaction,bis(2,2,2-trinitroethyl)substituted product of DAAF and single/bis(2,2,2-trinitroethyl)substituted products of DAOAF were synthesized and further nitrated using the mixture of 100%nitric acid and acetic anhydride.Resulting bis(2,2,2-trinitroethyl)nitramino derivatives were found to have excellent detonation properties.The structures of all products were confirmed by X-ray crystallographic analyses.The resulting new high nitrogen energetic compounds were characterized for thermal behaviors and explosive properties by experimental and theoretical methods.The results demonstrate that the way of azo and azoxy bonds bridging the high nitrogen backbones is useful to improve the thermal stabilities of energetic derivatives.2.The studies of synthesis and properties the energetic compounds based on the furoxan bridged bis(furazan)3-Amino-4-aminoximinofurazan was synthesized using commercially available dicyanopropane and hydroxylamine hydrochloride as starting materials,which was then treated with sodium nitrite and hydrogen hydrochloride to form 3-amino-4-chloroximinofurazan.The energetic compound based on furoxan bridged bis(furazan)(3,4-bis(4’-aminofurazano-3’-yl)furoxan)was prepared under thermal conditions by losing HCl followed by[4+2]ring-closure reaction of 3-amino-4-chloroximinofurazan.The single/bis(2,2,2-trinitroethyl)substituted products of 3,4-bis(4’-aminofurazano-3’-yl)furoxan were obtained by the condensation reactions of the amino group with 2,2,2-trinitroethanol.The bis(2,2,2-trinitroethyl)nitramino derivatives were obtained by nitrating the bis(2,2,2-trinitroethyl)substituted products.Besides,3,4-bis(4’-nitraminofurazano-3’-yl)furoxan,synthesized from nitrating 3,4-bis(4’-aminofurazano-3’-yl)furoxan by using 100%nitric acid was found to be unstable and slowly decomposed in the ether solution.To stabilized 3,4-bis(4’-nitraminofurazano-3’-yl)furoxan,a series of energetic salts were obtained by reaction with various bases.The resulting new energetic compounds were structurally characterized by X-Ray diffraction studies and,thermal behavior and explosive properties were determined by experimental and theoretical methods.The results demonstrate that derivatives based on trinitroethyl moieties exhibit excellent detonation properties and good thermal stabilities.Besides,the energetic salts also show excellent detonation properties,some of these salts with good thermal stabilities and high sensitive values,have the practical application value.3.The studies of synthesis and properties on the energetic compounds based on 1,2,4-oxadiazole3,5-Diamino-1,2,4-oxadizaole was synthesized in a high yield using sodium dicyanamide and hydroxylammonium hydrochloride as starting material.Reaction of 3,5-diamino-1,2,4-oxadizaole with two equivalents of trinitroethanol resulted in single 3-trinitroethyl substituted product only.To intensify the activity of amino group at 5-poisiton,single trinitroethyl substituted product was further reacted with trinitroethanol in the presence of diluted hydrochloric acid.Unfortunately,the 1,2,4-oxadizaole ring was opened under then acid condition.In order to convert 5-amino group of mono(trinitroethyl)substituted product to more energetic nitramino moiety,it was treated with 100%nitric acid but unfortunately,the 1,2,4-oxadizaole ring was also opened.The resulting trinitroethylamino and ring-opening compounds were investigated by IR,multiple NMR for structural characterization and were confirmed by X-ray crystallographic analyses.The thermal behaviors and explosive properties of resulting energetic derivatives were also investigated by experimental and theoretical methods.3-amino-4-(5-methyl-1,2,4-oxadiazole-3-yl)furazan was synthesized by condensation between 3-amino-4-aminoximinofurazan and acetamide under high temperature.And the trinitroethyl group was introduced into the furazan ring by Mannich reaction,and 3-(2,2,2-trinitroethylamino)-4-(5-methyl-1,2,4-oxadiazole-3-yl)furazan was obtained.A low melting trinitroethyl-nitramino derivative(with melting point even lower than room temperature)was synthesized by nitration of 3-(2,2,2-trinitroethylamino)-4-(5-methyl-1,2,4-oxadiazole-3-yl)furazan using mixture of 100%nitric acid and acetic anhydride.The amino group on 3-amino-4-(5-methyl-1,2,4-oxadiazole-3-yl)furazan was nitrated by 100%nitric acid to form nitramino group.In addition,a series of energetic salts were synthesized based on nitramino group.The new resulting compounds were characterized by 1H NMR,13C NMR and IR.The introduction of methyl group led to the decrease in the detonation properties,but it made them insensitive toward impact and friction.Diethyl 2,2’-(1,3,4-oxadiazole-2,5-diyl)diacetate was nitrated by the mixture of the nitric acid and sulfuric acid,the methylene group was nitrated to dinitromethylene group whic h was reacted with ammonia aqueous.The ammonium salt was formed which was reacted with silver nitrate,and the silver salt was obtained.The silver salt was reacted with a series of hydrochloride salt to get energetic salts based on(1,3,4-oxadiazole-2,5-diyl)bis-(dinitromethanide).The ammonium salt was acidified by concentrated sulfuric acid to form the neutral compound 2,5-bis(dinitromethyl)-1,3,4-oxadiazole which was reacted with a series of weak base.The guanidinium salt,ammonium guanidinium salt and 1,5-diamino tetrazolium salt were obtained.The new resulting compounds were characterized by 1H NMR,’3C NMR and IR.The structures of neutral compounds and some energetic salts were further confirmed by X-ray crystallographic analyses.Besides,the thermal behaviors and explosive properties of resulting energetic derivatives were also investigated.4.The studies of synthesis and properties on the energetic compounds based on 1,4,2,5-dioxazine bridged bis(furazan)3,6-Bis(4-amino-1,2,5-oxadiazole-3-yl)-1,4,2,5-dioxazine was synthesized by cyclization reactions of two molecules of 3-amino-4-chloroximinofurazan under basic condition(K2CO3).Trinitroethyl and nitramino groups were further introduced in the furazan rings using previously mentioned procedures.The introduction of trinitro groups can enhance the oxygen balance,and the nitramino groups can improve the detonation properties.Nitration of the derivatives based on trinitroethyl further improve the detonation properties of the corresponding compounds.Some structures were confirmed by X-ray crystallographic analyses.Besides,it is indicated that compounds based on 1,4,2,5-dioxazine bridged bis(furazan)exhibited excellent detonation properties but were sensitive towards impact and friction.5.The studies of synthesis and properties on the energetic compounds based on 3,6-diamino-1,2,4,5-tetrazine bridged bis(furazan)3,6-Bis(3-amino-1,2,5-oxadiazol-4-ylamino)-1,2,4,5-tetrazine(BOAT)was synthesized by using guanidine nitrate,hydrazine hydrate,acethylacetone and 3,6-bis(3,5-dimethylpyrazol-l-yl)-1,2,4,5-tetrazine(BT)as starting materials.3,6-bis(3-(2,2,2-trinitroethylamino-1,2,5-oxadiazole-4-ylamino)-3,6-diamino-1,2,4,5-tetrazine(BTAOT)was synthesized by reacting BOAT with 2,2,2-trinitroethanol.The derivatives of nitramino and trinitroethyl nitramino with excellent properties were synthesized by nitrating BOAT and BTOAT with 100%nitric acid.The compounds were characterized by 1H NMR,13C NMR and IR spectroscopy.In addition,the structures of neutral compounds and some energetic salts were further confirmed by X-ray crystallographic analyses.The results demonstrate that introduction of trinitroethyl moieties can enhance the energetic performance of tetrazine based energetic compounds.Many strong inter and intramolecular hydrogen bonds were observed in the crystal structures of these energetic compounds based on 3,6-diamino-1,2,4,5-tetrazine bridged bis(furazan),which contribute significantly towards their higher thermal stability and reduced sensitivity towards impact and friction.