Synthesis And Properties Of Several Nitrogen-Enriched High-Energy Triazoles

The molecular structure of triazole nitrogen-rich energetic compounds has N=N bond and C=N bond,the molecular structure is stable.It has the advantages of high heat of formation and environmental protection of combustion products.Its performance can be further improved by functionalization of detonating groups.This paper mainly includes the synthesis and performance research of two triazole nitrogen-rich energetic compounds1-trinitromethyl-3-nitro-1,2,4-triazole（TNMNT）and 2-methyl-4,5-dinitro-1,2,3-triazole-1-oxide（DNMTO）.The specific work is as follows:（1）Based on density functional theory,the density and formation enthalpy of TNMNT and DNMTO were predicted theoretically at B3PW91/6-31G**level using Gaussian09software;The predicted values of solid phase formation enthalpy were 259.3 k J/mol and321.56 k J/mol,respectively;the K-J equation is used to predict the molecular detonation performance,the theoretical density,theoretical detonation velocity and theoretical detonation pressure of TNMNT are 1.925 g/cm~3,8994 m/s and 37.3 GPa,respectively,the results show that the presence of trinitromethyl group leads to excellent molecular detonation performance;the calculated theoretical density,theoretical detonation velocity and theoretical detonation pressure of DNMTO are 1.793 g/cm~3,8889 m/s and 34.9 GPa,respectively,the results show that its density is low,but the detonation performance is not affected by the presence of coordinated oxygen.The bond dissociation energy and impact sensitivity of the two compounds were predicted,and the results showed that the thermal stability and impact sensitivity of the two compounds were better,indicating that the compounds had better safety performance.（2）Using 3-nitro-1,2,4-triazole as raw material and KBr as catalyst,1-acetonyl-3-nitro-1,2,4-triazole（ANT）,optimized reaction conditions:the reaction solvent DMF was reacted at a reaction temperature of 70℃for 3 h,n（NT）:n（chloroacetone）=1:4,and the product yield reached 38%;Then the target product TNMNT was prepared by nitration reaction,and the optimal reaction conditions were determined:the reaction temperature was25℃,reaction time was 36 h,V（HNO₃）:V（concentrated sulfuric acid）=1:3,and the product yield reached 43%.The results show that the use of low-toxic chloroacetone to replace the original bromoacetone is less toxic and harmless,improves the experimental safety,improves the substitution reaction conditions,replaces the original acetone reaction system with high boiling point solvent DMF,and increases the reaction temperature.The substitution reaction time is greatly shortened to 3 h,and the high acid ratio will have a positive impact on the nitrification reaction and shorten the nitration reaction time;The reaction mechanism was studied,and the product structure was characterized by infrared,nuclear magnetic and other characterization methods,and it was determined to be the target product;The TNMNT single crystal was grown by the solvent evaporation method,and it was found that it is a monoclinic crystal structure,belonging to the space group of P 21/c.The results show that due to intermolecular hydrogen bonding,its crystal density is 1.927 g/cm~3,which meets the requirement of higher energy density.（3）Using glyoxal as raw material,react with methyl hydrazine and hydroxylamine hydrochloride through condensation oximation reaction,the 2-methyl-1,2,3-triazole-1-oxide（MTO）was synthesized directly by copper sulfate-pyridine-water catalytic cyclization without separation,and the optimal reaction conditions:n（glyoxal）:n（hydroxylamine hydrochloride）:n（methyl hydrazine）=1:1:1（0.04 mol）,the amount of sodium carbonate is2.23 g（0.021 mol）,the amount of copper sulfate was 40 g,the reaction time was 0.5 h,the reaction temperature was 100℃,and the product yield was 21%;then the target product DNMTO was prepared by nitration reaction,and the optimal reaction conditions were determined:the reaction temperature was 100℃,The reaction time was 0.5 h,V（HNO₃）:V（concentrated sulfuric acid）=1:3,and the product yield reached 80%.The results show that the one-pot synthesis of the intermediate MTO simplifies the experimental steps,and the pulse ultrasonic liquid-liquid extraction method is introduced in the extraction process,which improves the product yield,indicating that this method can effectively improve the extraction efficiency of energetic compounds;The reaction mechanism was studied,and the product structure was characterized by infrared,elemental analysis and other characterization methods,and it was determined to be the target product;The DNMTO single crystal was obtained by solvent evaporation method.It was found to be an orthorhombic crystal structure,belonging to the space group of P/bac.Its crystal density was 1.729 g/cm~3,which was basically consistent with the predicted theoretical density.（4）According to the method specified in GJB772A-97,the mechanical sensitivity of the synthesized products was tested by the characteristic drop height method and the explosion probability method.The characteristic drop height H₅₀of TNMNT is 21.3cm,and the explosion probability of friction sensitivity is 56%.The sensitivity is high,but the mechanical sensitivity is somewhat reduced due to the presence of the triazole parent ring compared with other molecular structures,and the combination of the two has a complementary effect;To test the thermal properties of TNMNT,the melting point is 100.5℃,and the decomposition peak temperature is 164.6℃.According to the measured decomposition peak temperature and the corresponding formula at different heating rates,the activation energy is calculated to be104.44 k J/mol,and the pre-exponential factor A=1.36×10¹²min^-1,the results showed that compared with the raw material 3-nitro-1,2,4-triazole,the introduction of trinitromethyl resulted in a lower melting point of the compound,and although its energy was higher,its thermal stability was weaker than that of C-nitro;The characteristic drop height H₅₀of DNMTO is measured to be 53 cm,and the explosion probability of friction sensitivity is 12%.The results show that there are explosion-suppressing groups such as methyl groups in the molecule,and the molecular structure is stable and symmetrical,which makes its mechanical sensitivity more insensitive than TNMNT;To test the thermal properties of DNMTO,the melting point is 130.5℃,and the decomposition peak temperature is 245℃.The activation energy is calculated to be 208.8 k J/mol,and the pre-exponential factor A=1.34×10²¹min^-1,the results show that the introduction of methyl can reduce the melting point of the compound,and the symmetry of the molecular structure leads to the excellent thermal properties of the compound.