Substituent effect on the molecular stability, group interaction, detonation performance, and thermolysis mechanism of nitroamino-substituted cyclopentanes and cyclohexanes

Abstract

Density functional theory (DFT) method has been employed to study the effect of nitroamino group as a substituent in cyclopentane and cyclohexane, which usually construct the polycyclic or caged nitramines. Molecular structures were investigated at the B3LYP/6-31G** level, and isodesmic reactions were designed for calculating the group interactions. The results show that the group interactions accord with the group additivity, increasing with the increasing number of nitroamino groups. The distance between substituents influences the interactions. Detonation performances were evaluated by the Kamlet-Jacobs equations based on the predicted densities and heats of formation, while thermal stability and pyrolysis mechanism were studied by the computations of bond dissociation energy (BDE). It is found that the contributions of nitroamino groups to the detonation heat, detonation velocity, detonation pressure, and stability all deviate from the group additivity. Only 3a, 3b, and 9a-9c may be novel potential candidates of high energy density materials (HEDMs) according to the quantitative criteria of HEDM (ρ ≈ 1.9 g/cm 3 , D ≈ 9.0 km/s, P ≈ 40.0 GPa). Stability decreases with the increasing number of N-NO 2 groups, and homolysis of N-NO 2 bond is the initial step in the thermolysis of the title compounds. Coupled with the demand of thermal stability (BDE > 20 kcal/mol), only 1,2,4-trinitrotriazacyclohexane and 1,2,4,5-tetranitrotetraazacyclohexane are suggested as feasible energetic materials. These results may provide basic information for the molecular design of HEDMs. density functional theory (DFT), substituent effect, monocyclic nitramine, high energy density material (HEDM), group interaction, detonation performance, thermal stability, bond dissociation energy (BDE) Cyclic nitramines, such as RDX (1,3,5-trinitro-1,3,5-triazacyclohexane) and HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane), are powerful solid explosives and propellants used extensively in both civilian and military fields. So far, there has been a significant history of interest in their structures and properties since they were first reported [1][2][3][4][5][6][7][8][9][10][11][12][13][14] . In order to obtain novel high energy density materials (HEDMs), without a doubt, scientists pay considerable attention to other cyclic nitramines all the while and manage to attach the NO 2 group essentially needed for the combustion (the so-called energetic function) to the heterocyclic rings to form energetic materials with good explosive performance [15][16][17][18][19][20][21] . For instance, 1,3,3-trinitroazetidine (TNAZ) is one of such famous HEDMs in use for both military and civilian industries [17,18] . However, when the nitro groups are substituted on other heterocyclic rings, how about the per-

Crystal structure, detonation performance, and thermal stability of a new polynitro cage compound: 2, 4, 6, 8, 10, 12, 13, 14, 15-nonanitro-2, 4, 6, 8, 10, 12, 13, 14, 15-nonaazaheptacyclo [5.5.1.13, 11. 15, 9] pentadecane

“…The empirical Kamlet-Jacobs equations [13] widely employed [2][3][4][14][15][16][17][18][19][20][21][22] to estimate the detonation velocity and detonation pressure, the important parameters reflecting the explosive performance of energetic materials were used: …”

“…(Table 6) Pyrolysis mechanism and thermal stability Thermal stability is a fundamental property of energetic materials. Nitro groups are often the primary cause of initiation reactivity of polynitro compounds [15,16,[19][20][21]. Due to the symmetry of the structure of NNNAHP, BDEs of two different N-NO 2 bonds with smaller bond populations, i.e., N(1)-NO 2 and N(3)-NO 2 are calculated.…”

A theoretical investigation on the structures, densities, detonation properties and pyrolysis mechanism of the nitro derivatives of toluenes

“…However, for those unsynthesized or hypothetical explosives, their Q and 0 cannot be evaluated from experimental measures. Therefore, in the molecular design of HEDC, in order to predict the detonation properties, we have recommended the modified K-J equations based on the calculation results of quantum chemistry [5][6][7][8][9][10][11][12][13][14][15][16][17].…”

“…However, the previous molecular design of HEDM lacks quantitative criteria of identification, which is difficult to identify and to filtrate effectively HEDC. Therefore, in the past several years, our group has carried out a series of investigations on the molecular design for many typical categories of energetic compounds [5][6][7][8][9][10][11][12][13][14][15][16][17]. Considering the practical requirements and based on the results of these studies, a quantitative criteria associated both energy (including , D, and P) and stability (BDE of the trigger bond) requirements, i.e., ≈ 1.9 g/cm 3 , D ≈ 9.0 km/s, P ≈ 40.0 Gpa, and BDE ≈ 80-120 kJ/mol [18], are proposed and employed to filtrate and recommend potential HEDCs [14].…”

Some Novel Tricyclic Caged-Nitramines - A DFT Study

“…Substituent effects on the molecular stability, group interaction, detonation performance, and thermolysis mechanism of certain nitramines were reported [12]. On the other hand, design strategy from linear to cyclic to caged molecules were discussed by Yang et al [13].…”