Oxygen-Rich Energetic Compounds:Molecular Design And Theoretical Study

The oxygen-rich energetic compounds are widely used in propellants and explosives.It is necessary to perform systematic and in-depth studies on these materials.Theoretical methods such as density functional theory have been used to study a lot of oxygen-rich compounds(such as energetic salts,nitro substituted cyclic compounds and trinitromethyl substituted compounds).The structures,stabilities,detonation performance and physicochemical properties have been systematically investigated to search for the relationships between structure and property and to screen the compounds with great performance.The synthetic routes of the selective compounds were proposed and their feasibility was predicted based on theoretical calculations to provide guidance for experiment.The main contents are as following:1.The structures,intramolecular hydrogen bonding interactions,changes in enthalpy(?rHm)and in Gibbs free energy(?rGm)for the formation reaction,and detonation performance of hydrazinium dinitramide(HDN)have been investigated.The predicted ?rGms show that preparation of HDN is easier than HNF but harder than ADN.Compared to ADN and HNF,HDN possesses stronger intramolecular hydrogen bonding interactions,which makes it have the higher thermal stability.Detonation performance of HDN is better than that of ADN.The simple synthetic route,high thermal stability and good detonation performance of HDN suggest that it is a promising oxidizer.2.The effects of H2O on HNF in the gaseous,solution and solid sates have been investigated.The intramolecular hydrogen bonding interactions of HNF in the gaseous and solution states are weakened by H2O,and H2O weakens the C-NO2 bond and decreases the number of hydrogen bonds of HNF in solid state.In a word,H2O decreases the stability of HNF in gas,solution and solid states.The intermolecular hydrogen bonds between HNF and H2O should be responsible for the moisture of HNF,and finding a way to weaken this interaction is the key to decrease the moisture of HNF.3.According to the results of ?rHm and ?rGm for the neutralization reaction,hydrogen bonding interaction,lattice energy,and detonation performance,HN(NO2)2 is more suitable than HNO3,HClO4 and HC(NO2)3 as an oxygen-rich acid to prepare energetic salts and 5-aminotetrazole is more suitable than 4-amino-1,2,4-triazole and 1-amino-1,2,4-trizole as a nitrogen-rich base to prepare energetic salts.Introduction of-N3 is better than-CH3,-NH2,-NF2 and-NO2 into the framework of 3,3'-amino-4,4'-azo-1,2,4-triazoles(DAAT)for forming new base to prepare energetic salts.4.2-nitroepoxyethane,2,3-dinitroepoxyethane,2,2,3-trinitroepoxyethane and 2,2,3,3-tetranitroepoxyethane can be thermally prepared by stepwise nitration of epoxyethane.2,2,3,3-tetranitroaziridine can be thermally prepared by cyclization of ethanolamine and nitration of aziridine.The bond dissociation energies(BDEs)of the five nitro compounds are larger than 117 kJ/mol,indicating that their thermal stabilities are acceptable.The composite explosive mixed by 2,2,3-trinitroepoxyethane,2,2,3,3-tetranitroepoxyethane,or 2,2,3,3-tetranitroaziridine with RDX possesses great detonation performance(detonation velocity D = 9.14?9.45 km/s,detonation pressure P = 37.30-41.04 GPa,specific impulse Is =280?285 s).5.Various groups-CH3,-OCH3,-NH2,-OH,-NO2 and-ONO2 are respectively introduced to 5-nitro-3-trinitromethyl-1H-1,2,4-triazole(NTMT).The pyrolysis initiation bonds of NTMT and all its derivatives but NTMT-ONO2 are the C-NO2 bond of the trinitromethyl group.The introduced groups slightly affect the stability of the C-NO2 bond.The impact sensitivities of all compounds but NTMT-NO2 and NTMT-ONO2 are lower than that of RDX.The detonation performances of NTMT,NTMT-OCH3,NTMT-OH and NTMT-NH2 are similar to that of RDX,indicating that they can be used as single compound explosives.The composite explosive mixed by RDX and NTMT,or its derivatives NTMT-OH,NTMT-NH2,NTMT-NO2,NTMT-ONO2 has the great detonation properties.The approp:r:iate stability and great detonation performance show that NTMT,NTMT-OH and NTMT-NH2 are promising oxidizers.6.The maximum electron densities at the critical points(?max)of two N-O bonds of the nitro group can be employed to predict the stability of nitro compounds.The larger ?max corresponds to the higher total energy of isomer,the smaller BDE,the higher impact sensitivity,the more rigorous experimental conditions,the lower productivity and the slower reaction rate.Compared to other methods used to predict the stability of nitro compounds,the method using ?max is more timesaving,more widely applicable and less sensitive to theoretical level.