The Rational Synthesis,Characterization,Thermal Properties And Theoretical Investigation Of Nitrogen-richheterocycles Based On 4,4?-azo-1H-1,2,4-triazol-5-one

The introduction of the azo-group?—N=N—?into a molecule can make it exhibit higher nitrogen content,higher positive heat of formation andhigher density.In the field of advanced energetic materials,the nitrogen-rich azole compounds are widely studied in this waybymanyresearchers.Inthiswork,ninecompoundsof4,4?-Azo-1H-1,2,4-triazol-5-one?ZTO?were designed and synthesized.The detailed research contents are summarized as follows:?1?Due to the faintly acid of ZTO,six nitrogen-rich salts of ZTO were prepared through acid-alkalireaction and ion exchange reaction.The six salts are bis?guanidinium?salt[G₂?ZTO?],bis?diaminoguanidinium?salt[DAG₂?ZTO?],ethylene-diamine salt[EDA?ZTO?],1,3-propanediamine salt[PDA?ZTO?],1,4-butanediamine salt[BDA?ZTO?],mono-sodium salt[Na?ZTO?·2H₂O].And three derivatives were obtained by electrophilic substitution reaction.They are bis?benzoyl?-4,4?-Azo-1H-1,2,4-triazol-5-one?DBZTO?,bis?4-methylbenzoyl?-4,4?-Azo-1H-1,2,4-triazol-5-one[D?4-MB?ZTO]and bis?3-methylbenzoyl?-4,4?-Azo-1H-1,2,4-triazol-5-one[D?3-MB?ZTO].The synthetic processes of the nine compounds were simple,the yields were high and the products were easy to be separated and purified.The products were characterized by EA,FT-IR and NMR.Compounds G₂?ZTO?and Na?ZTO?·2H₂O were additionally characterized by single crystal X-ray diffraction.?2?The thermal behaviors of the nine products were studied by DSC and TG/DTG.The results indicate that all compounds have good thermal stability.All the ZTO salts have lower decompositionpeak temperature than their precursor ZTO,which indicates that the decompositiontemperature is decreased by salt-forming reaction.Moreover,the main decompositiontemperature is reduced with an increasing number ofmethylene groups in the three diamine salts of ZTO.The thermal decomposition kinetic parameters and kinetic equations of the new compounds were calculated and obtained employed by Kissinger method,Ozawa method and integral equation.?3?To evaluate thermal safety of these compounds,the thermal parameters and thermodynamic functionsfortheir mainexothermic decomposition process were calculated,such as,self-accelerating decomposition temperature(T_e0),thermal ignition temperature(T_be0),critical temperature of thermal explosion(T_bp0).And thermodynamic functions,for instance,entropy of activation??S^??,enthalpy of activation??H^??and free energy of activation??G^??.?4?The specific heat capacity changes with temperature ranging from 283 to 333 K of the five compounds were determined using the continuous mode of Micro-DSC?micro-calorimeter.?5?The constant-volume combustion heats??_cU?for these compounds were measured by IKA C5000 oxygen bomb calorimeter.The experimental values of the standard molar enthalpy of formation??_fH_m^??can be calculated for the new products according to Hess' s law.?6?Gaussian 09 W and Multiwfn program have been employed to study a series of nitrogen-richheterocyclic salts of ZTO including previously reported based on ZTOsystemically.The volumes,densities and solid-phase heats of formation?HOFs?were corrected.Detonation parameters and impact sensitivities(h₅₀)were further predicted.