Study On The Structure And Stability Of N₈ Double Five Membered Rings And Their Protonation

In recent years,the high energy density properties of nitrogen-rich compounds have been the research hotspot of chemists.The main concern of nitrogen-rich compounds is that they have a large number of nitrogen-nitrogen single bonds and nitrogen-nitrogen double bonds.When they form three bonds,they are accompanied by a large amount of energy release.This substance is called high energy density substance?HEDM?.Therefore,according to its nature,HEDM can also be used as an explosive,propellant,gas generator or a component of the sudden sense initiating explosive,because its product is N₂,but also has the characteristics of environmental protection.These advantages make it widely used in military and civilian fields.In recent decades,nitrogen-rich compounds have been reported in a large number of literatures,which makes the chemical significance of experimental synthesis and theoretical design of nitrogen-rich high energy density materials?HEDMs?very important.As everyone knows,When it comes to nitrogen-rich high energy density materials,the first thing to consider is their stability and heat of formation.This makes the development of nitrogen-rich high-energy materials will encounter many problems,and at the same time will have a high risk.In this paper,a new high energy density compound,N8 double five membered rings pentacyclic substitution doped with different substituents,is studied by theoretical calculation method.The structure and stability of N₈ double five membered rings pentacycles and the geometric structure and stability of compounds doped with H,-CH₃,-NH₂,N₃ and CN were studied.In this paper,density functional theory?DFT?is used to study the geometric structure and the isomeric and decomposition potential energy surfaces of isomers in the whole process,and to determine their thermodynamic and dynamic stability.The calculated results can be used as a theoretical reference for laboratory synthesis and avoid the possible risks in the process of experiment.When different substituents?H,-CH₃,-NH₂,N₃,CN?are doped into N₈ double-five-membered-ring structure,the isomerization and decomposition reaction paths of the isomers are determined by analyzing the potential energy surface of the system,and the dynamic stability of the system is determined by decomposition barrier.It is found that the stability of N₈H⁺system is lower than that of N₈ double five-ring system due to the destruction of structural symmetry when doped with H ion?N₈H⁺?.When doped with two H ions(N₈H₂²⁺),the decomposition minimum barrier of A structure with the best thermodynamic stability is 47.1 kcal?mol^-1,which has very high kinetic stability.When three H ions(N₈H₃³⁺)and four H ions(N₈H₄⁴⁺)were doped,the stability of the whole system was not as good as that of N₈H₂²⁺system.It can be predicted that the double protonation process of bis-pentacyclic nitrogen compounds will provide a reliable possibility for their application in laboratory,and this idea will promote the theoretical research of nitrogen-rich compounds.It will also provide a more theoretical and comprehensive basis for future experimental synthesis.