Studies On The Synthesis And Properties Of Imidazole Energetic Materials

Imidazole energetic materials are one of the active research directions in the field of explosives synthesis,which have the characteristics of high nitrogen content,high enthalpy of formation,and excellent thermal stability.In this dissertation,the synthesis and properties of 1-amino-2,4-dinitroimidazole?ADNI?and imidazole bis-cationic energetic salts were studied.Starting from imidazole,2,4-dinitroimidazole was synthesized via C-4 nitration,N-nitration,and rearrangement.N-Boc protection of hydroxylamine,then introduction of O-sulfonyl,O-phenyl,or O-benzoyl,and further hydrolysis with CF₃COOH or HClO₄,gave a series of amination reagents,such as O-?4-methylbenzenesulfonyl?hydroxylamine,O-?2,4,6-trimethylbenzenesulfonyl?hydroxylamine,O-?p-nitrobenzoyl?hydroxylamineand O-?2,4-Dinitrophenyl?hydroxylamine.Besides,O-?diphenylphosphinyl?hydroxylamine was synthesized by direct reaction of hydroxylamine and diphenylphosphinyl chloride without any protection.The amination of2,4-dinitroimidazole was studied using hydroxylamine-O-sulphonic acid,as well as the above hydroxylamine derivatives as amination reagents.Finally,1-amino-2,4-dinitroimidazole?ADNI?was successfully synthesized in a 72.1%yield from 2,4-dinitroimidazole.All the target products and intermediates were characterized by UV-Vis,FT-IR,ESI-MS,or NMR.Starting from 2-methylimidazole,3,3'-methylene-bis?2-methyl-1-nitroxyethyl-imidazolium?dinitrate was synthesized as a bis-cationic energetic salt by methylene-bridging,quaternization,and nitration reactions.Then metathesis reactions of 3,3'-methylene-bis?2-methyl-1-nitroxyethyl-imidazolium?dinitrate provided bis-cationic energetic salts with a picrate,a dinitramide,a 3,5-dinitro-1,2,4-triazolate,or a 5-nitrotetrazolate anion.All the energetic salts were characterized by ultraviolet visible spectrum?UV-Vis?,infrared spectrum?IR?,mass spectrum?MS?,nuclear magnetic resonance?NMR?,elemental analysis,and thermo-gravimetric analysis?TG-DTG?.TG-DTG shows that the bis-cationic energetic salts have a good thermal stability,of which the decomposition temperatures are above 169 ^oC and the thermal decomposition peak temperatures are close to 200 ^oC for the first decomposition stage.Interestingly,the bis-cationic energetic salts apart from 5-nitrotetrazolate have a better thermal stability than the corresponding mono-cationic imidazolium energetic salts.Besides,all the bis-cationic energetic salts have a higher melting point than the corresponding mono-cationic energetic salts.Meanwhile,some bis-cationic imidazolium energetic salts have a higher density than the corresponding mono-cationic energetic salts.The standard enthalpies of formation and detonation properties of the energetic salts were also estimated by Kamlet-Jacobs equation,showing that the energetic salts have good detonation performances.The detonation velocitiesanddetonationpressuresof3,3'-methylene-bis?2-methyl-1-nitroxyethylimidazolium?-di?3,5-dinitro-1,2,4-triazolate?and 3,3'-methylene-bis?2-methyl-1-nitroxyethyl-imidazolium?-di?5-nitrotetrazolate?are between those of2,4,6-trinitrotoluene?TNT?and 1,3,5-trinitroperhydro-1,3,5-triazine?RDX?.