Synthesis,Substitution Sequence And Properties Of Asymmetric 1,2,4,5-tetrazines

Energetic compounds,a kind of compounds that release a lot of energy under external stimulation,are widely used in military and aerospace fields currently.Nitrogen-rich heterocyclic energetic materials have attracted wide attention because of their high energy and low sensitivity,among which 1,2,4,5-tetrazine energetic materials are one of the representative compounds.In this paper,the reaction mechanism of asymmetric 1,2,4,5-tetrazine was mainly studied,and several tetrazine compounds were prepared and their thermal behaviors were studied.In order to synthesize 3-nitroguanidine-6-amino-1,2,4,5-tetrazine（NAT）as the target compound,two synthetic routes were designed,and one route was used to prepare NAT.It was found that the substitution order of different substituents had great influence on the successful synthesis of asymmetric 1,2,4,5-tetrazine compounds.Then,two other asymmetric1,2,4,5-tetrazine organic compounds were synthesized,which were 3,6-diamino-1,2,4,5-tetrazine（DAT）and 6-nitro-1,2,4,5-tetrazine-3-one（NTz O）,and the potassium salt of NGTz O was prepared Some compounds were characterized by elemental analysis（EA）,Fourier transform infrared（FT-IR）and nuclear magnetic resonance（HNMR）.Single crystals of ADT,NGTz O potassium salt and DTO were cultured and their spatial configurations were determined.Gaussian16 was used to treat ADT,3,6-diamino-1,2,4,5-tetrazine（DAT）,NAT,6-nitroguanidine-1,2,4,5-tetrazine-3-one（NGTz O）,6-amino-1,2,4,5-one by comparing the frontier orbital energy and static potential of compounds substituted by different substituents,the influence of electronic effect of substituents on the substitution order of tetrazine compounds at 3 and 6 positions is studied:when the unilateral substitution at 3 position is the substituent for electron donor effect,the substitution reaction at 6 position is more likely to occur;When the 3-position unilateral substitution is a substituent with electron-withdrawing effect,the 6-position substitution is difficult or impossible to occur.Differential scanning calorimetry（DSC）and thermogravimetric-derivative method（TG-DTG）were used for thermal analysis of five newly synthesized compounds or salts.By calculating the DSC curves of three compounds at four different heating rates,the thermal decomposition kinetic parameters are obtained,and the thermal decomposition kinetic equation is obtained,thereby calculating the self-accelerating decomposition temperature of the five compounds during the thermal decomposition process(T_SADT),thermal explosion critical temperature(T_bp),thermal ignition temperature(T_be),and further evaluated their thermal stability.