Comparative theoretical studies of energetic azo s-triazines

In this work, the properties of the synthesized high-nitrogen compounds 4,4',6,6'-tetra(azido)azo-1,3,5-triazine (TAAT) and 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine (TAHT), and a set of designed bridged triazines with similar bridges were studied theoretically to facilitate further developments for the molecules of interests. The gas-phase heats of formation were predicted based on the isodesmic reactions by using the DFT-B3LYP/AUG-cc-PVDZ method. The estimates of the condensed-phase heats of formation and heats of sublimation were estimated in the framework of the Politzer approach. Calculation results show that the method gives a good estimation for enthalpies, in comparison with available experimental data for TAAT and TAHT. The crystal density has been computed using molecular packing calculations. The calculated detonation velocities and detonation pressures indicate that -NF(2), -NO(2), -N═N-, and -N═N(O)- groups are effective structural units for improving the detonation performance of the bridged triazines. The synthesized TAAT and TAHT are not preferred energetic materials due to their inferior detonation performance. The p→π conjugation effect between the triazine rings and bridges makes the molecule stable as a whole. The electrostatic behavior of the bridged triazines is characterized by an anomalous surface potential imbalance when incorporating the strongly electron-withdrawing -NF(2) and -NO(2) groups into the molecule. An analysis of the bond dissociation energies shows that all these derivatives have good thermal stability over RDX and HMX, and the -NH-NH- bridge is more helpful for improving the stability than -N═N(O)- and -N═N- bridges. Considering the detonation performance and thermal stability, three bridged triazines may be considered as the potential candidates of high-energy density materials (HEDMs).     

Theoretical investigations on structure,density, detonation properties,and sensitivity of the derivatives of PYX

The ? NH₂, ? NO₂, ? N₃, ? NHNO₂, and ? ONO₂ substitution derivatives of PYX (2,6‐bis(picrylamino)‐3,5‐dinitropyridine) were studied at the B3LYP/6‐31G** level of density functional theory. The sublimation enthalpies and heats of formation (HOFs) in gas phase and solid state of these compounds were calculated. The theoretical predicted density (ρ), detonation pressure (P), and detonation velocity (D) showed that these derivatives have better detonation performance than PYX. The effects of substituent groups on HOF, ρ, P, and D were discussed. The order of contribution of various groups to P and D was ? ONO₂ > ? NO₂ > ? NHNO₂ > ? N₃ > ? NH₂. Sensitivity was evaluated using the frontier orbital energies, bond orders, bond dissociation enthalpies (BDEs), and characteristic heights (h₅₀). The trigger bonds in the pyrolysis process for these PYX derivatives may be Ring‐NO₂, NH? NO₂, or O? NO₂ varying with the substituents. The h₅₀ of most compounds are larger than that of CL‐20, and those of ? NH₂, ? NO₂, and most ? ONO₂ derivatives are larger than that of RDX. The BDEs of the trigger bonds of all but the ? ONO₂ derivatives are sufficiently large. Taking both detonation performance and sensitivity into consideration, some derivatives of PYX may be good candidates of explosives. © 2012 Wiley Periodicals, Inc.     

Computational DFT studies on a series of toluene derivatives as potential high energy density compounds

Based on the full optimized molecular geometric structures at B3LYP/6-31G**, B3LYP/6-31+G**, B3P86/6-31G**, and B3P86/6-31+G** levels, the densities (ρ), detonation velocities (D), and pressures (P) for a series of toluene derivatives, as well as their thermal stabilities, were investigated to look for high energy density compounds (HEDCs). The heats of formation (HOFs) are also calculated via designed isodesmic reactions. The calculations on the bond dissociation energies (BDEs) indicate that the BDEs of the initial scission step are between 48 and 59 kcal/mol, and pentanitrotoluene is the most reactive compound, while 2,4,6-trinitrotoluene is the least reactive compound for toluene derivatives studied. A good linear relationship between BDE/E and impact sensitivity is also obtained. The condensed phase HOFs are calculated for the title compounds. These results would provide basic information for the further studies of HEDCs. The detonation data of pentanitrotoluene show that it meets the requirement for HEDCs.     

Theoretical studies on a series of 1,2,3-triazoles derivatives as potential high energy density compounds

Based on the full-optimized molecular geometric structures at B3LYP/6-31G* and B3P86/6-31G* levels, the densities (ρ), detonation velocities (D), and pressures (P) for a series of 1,2,3-triazole derivatives, as well as their thermal stabilities, were investigated to look for high energy density compounds (HEDCs). The heats of formation (HOFs) are also calculated via designed isodesmic reactions. The calculations on the bond dissociation energies (BDEs) indicate that the BDEs of the initial scission step are between 53 and 70 kcal/mol, and 4-nitro-1,2,3-triazole is the most reactive compound, while 1-(2′,4′-dinitrophenyl)-5-nitro-1,2,3-triazole is the least reactive compound for 1,2,3-triazole derivatives studied. The condensed phase heats of formation are also calculated for the title compounds. These results would provide basic information for the further studies of HEDCs. The detonation data of 1-(3′,4′-dinitrophenyl)-4-nitro-1,2,3-triazole and 1-(2′,4′-dinitrophenyl)-4-nitro-1,2,3-triazole show that they meet the requirement for HEDCs.     

Theoretical Study on Nitroso-Substituted Derivatives of Azetidine as Potential High Energy Density Compounds

At the B3 PW91/6-311+G(d,p)//MP2/6-311+G(d,p) level, molecular densities, detonation velocities, and detonation pressures of nitroso substituted derivatives of azetidine with their thermal stabilities were investigated to look for high energy density compounds(HEDCs). It was found that the azetidine derivatives had high heat of formation(HOF) and large bond dissociation energy(BDE). Intramolecular hydrogen bonds were located in three molecules(1, 4, and 5), and the molecular stability were improved markedly as well. For 5 and 6, the detonation performances(D= 9.36 km/s and 10.80 km/s, P= 44.42 GPa and 60.70 GPa, respectively) meet requirements as high energy density compounds. This work may provide basic information for further study of title compounds.     

Molecular design and property prediction of a series of novel cyclotetramethylene tetranitramine derivatives as high energy density compounds

We constructed five novel cyclotetramethylene tetranitramine (HMX) derivatives based on the skeleton of HMX ring. The molecules were fully optimized at the B3LYP/6-311G (d) level. We designed isodesmic reactions to calculate their enthalpies of formation. Then, their heats of detonation, detonation velocities, and detonation pressures were calculated using the Kamlet-Jacobs equations on the theoretical densities and enthalpies of formation. Their oxygen balances were computed to estimate whether the title compounds are oxygen-enriched or oxygen-poor. Finally, their impact sensitivity values were evaluated via a simple equation reported in previous studies. In terms of the quantitative standard as high energy density compounds (HEDCs), the potential candidates of HEDCs were selected.     

Computational characterization of 2, 4, 6, 8, 10, 12, 13-heptaazatetracyclo [5.5.1.03,11.05,9]tridecanes as potential energetic compounds

The characters of high density and high heat of formation of cage molecules have attracted a lot of investigations as potential energetic materials. Several such compounds have been synthesized, e.g., octanitrocubane, hexanitrohexaazaisowurzitane (CL-20), and 4-trinitroethyl-2, 6, 8, 10, 12-pentanitrohexaazaisowurtzitane(TNE-CL-20). In the present study, a new cage compound, namely 2, 4, 6, 8, 10, 12, 13-heptaazatetracyclo [5.5.1.0^3,11.0^5,9] tridecane (HATT), was proposed. Density functional theory has been employed to study the geometric and electronic structures for a series of nitro derivatives of HATT at the B3LYP/6-31G(d,p) level. Thermodynamic properties derived on the basis of statistical thermodynamic principles are linearly correlated with the numbers of nitro group as well as the temperature. Detonation performance was evaluated based on the calculated densities and heats of formation. It is found that some title compounds have high densities of ca. 1.9 g cm^?3, detonation velocities over 9.0 km s^?1, and detonation pressures of about 40.0 GPa and may be novel potential candidates of high energy density compounds (HEDCs). Thermal stability and pyrolysis mechanism of the nitro HATTs were investigated by calculating the bond dissociation energies (BDE). In conjunction with the detonation performance and thermal stability, HATTs with no less than five nitro groups are recommended as the preferred candidates of HEDCs. These results provide basic information for the further studies of cage compounds.     

Looking for high energy density compounds applicable for propellant among the derivatives of DPO with -N3, -ONO2, and -NNO2 groups

The derivatives of DPO (2,5-dipicryl-1,3,4-oxadiazole) are optimized to obtain their molecular geometries and electronic structures at the DFT-B3LYP/6-31G* level. The bond length is focused to primarily predict thermal stability and the pyrolysis mechanism of the title compounds. Detonation properties are evaluated using the modified Kamlet-Jacobs equations based on the calculated densities and heats of formation. It is found that there are good linear relationships between density, detonation velocity, detonation pressure, and the number of azido, nitrate, and nitramine groups. According to the largest exothermic principle, the relative specific impulse is investigated by calculating the enthalpy of combustion (ΔH(comb)) and the total heat capacity (C(p,gases)). It is found that the introduction of -N(3), -ONO(2), and -NNO(2) groups could increase the specific impulses and II-4, II-5, and III-5 are potential candidates for High Energy Density Materials (HEDMs). The effect of the azido, nitrate, and nitramine groups on the structure and the properties is discussed.     

Computational study on energetic properties of nitro derivatives of furan substituted azoles

Density functional theory has been used to investigate geometries, heats of formation (HOFs), C-NO₂ bond dissociation energies (BDEs), and relative energetic properties of nitro derivatives of azole substituted furan. HOFs for a series of molecules were calculated by using density functional theory (DFT) and Møller–Plesset (MP2) methods. The density is predicted using crystal packing calculations; all the designed compounds show density above 1.71 g/cm³. The calculated detonation velocities and detonation pressures indicate that the nitro group is very helpful for enhancing the detonation performance for the designed compounds. Thermal stabilities have been evaluated from the bond dissociation energies. Charge on the nitro group was used to assess the impact sensitivity in this study. According to the results of the calculations, tri- and tetra-nitro substituted derivatives reveal high performance with better thermal stability.     

Tin-oxo clusters based on aryl arsonate anions

Reactions of Ph(3)SnOH or Ph3SnCl with aryl arsonic acids RAsO3H2, where R=C6H5 (1), 2-NH2C6H4 (2), 4-NH2C6H4 (3), 2-NO2C6H4 (4), 3-NO2C6H4 (5), 4-NO2C6H4 (6), 3-NO2-4-OHC6H3 (7), 2-ClC6H4 (8) and 2,4-Cl2C6H3 (9), gave 18 Sn-O cluster compounds. These compounds can be classified into four types: type A: [{(PhSn)3(RAsO3)3(mu3-O)(OH)(R'O)2}2Sn] (R=C6H5, 2-NH2C6H4, 4-NH2C6H4, 2-NO2C6H4, 3-NO2C6H4, 2-ClC6H4, 2,4-Cl2C6H3, and 3-NO2-4-OHC6H3; R'=Me or Et); type B: [{(PhSn)3(RAsO3)(2)(RAsO3H)(mu3-O)(R'O)2}2] (R=4-NO2C6H4, R'=Me); type C: [{(PhSn)3(RAsO3)3(mu3-O)(R'O)3}2Sn] (R=2,4-Cl2C6H3, R'=Me); type D: [{Sn3Cl3(mu3-O)(R'O)3}(2)(RAsO3)4] (R=2-NO2C6H4 and 4-NO2-C6H4; R'=Me or Et). Structures of types A and B contain [Sn3(mu3-O)(mu2-OR')2] building blocks, while in types C and D the stannoxane cores are built from two [Sn3(mu3-O)(mu2-OR')3] building blocks. The reactions proceeded with partial or complete dearylation of the triphenyltin precursor. These various structural forms are realized by subtle changes in the nature of the organotin precursors and aryl arsonic acids. The syntheses, structures, and structural interrelationship of these organostannoxanes are discussed.     

多硝基尿酸衍生物含能性质的理论研究

为了寻找兼具优异爆轰性能和良好热力学及动力学稳定性的高能材料, 本文设计了15个硝基尿酸化合物, 运用密度泛函理论, 对其性质进行了研究. 通过半经验的K-J方程和比冲量预测了其爆炸性能, 结果表明, 所设计分子的爆热、 分子密度、 爆炸速率和爆炸压强同硝基取代基数目之间存在较强的线性关系. 三硝基尿酸和四硝基尿酸衍生物的爆炸速率超过了8.0 km/s, 爆炸压强超过了30 GPa, 并且大多数衍生物的比冲量要高于目前经常使用的炸药黑索金. 通过计算N—NO₂键的解离能、 特征落高、 分子的自由空间预判了衍生物的稳定性和撞击感度, 结果显示, 绝大多数分子有大于80 kJ/mol的键解离能. 本文的理论结果可以为实验上设计合成新的高能材料提供一些有用的信息.     

几种新型六氮杂异伍兹烷衍生物结构与性能的理论预测—— 高能量密度化合物的寻求

以CN, NC, ONO2, N3, NH2, N2H, NHNH2, N4H和N4H3 9种含氮高能基团为取代基, 分别取代2,4,6,8,10,12-六氮杂异伍兹烷(IW)中亚氨基的6个H原子所形成的9种六氮杂异伍兹烷衍生物作为研究目标分子. 运用密度泛函理论, 在B3LYP/6-31G**水平上求得了它们的分子几何构型、电子结构、解离能(BDE)及IR谱等信息, 并设计等键反应计算了生成热( ). 基于统计热力学原理计算拟合了100～1200 K温度范围内体系的热力学函数, 利用Kamlet-Jacobs方程估算了它们的爆轰性能. 研究结果表明, 9种六氮杂异伍兹烷衍生物存在两种可能的热解引发类型. 在衍生物HNiIW, HBDAIW和HBAIW中, 可能的热解引发键是取代基内部的化学键, 而其余衍生物的热解引发键则可能是骨架N与取代基R之间N—R键. 另外, 硝酸酯基(ONO2)取代所得化合物HNiIW的密度ρ、爆速D及爆压p分别为1.998 g•cm－3, 9.71 km•s－1和44.47 GPa, 完全达到高能量密度化合物(HEDC)的基本要求, 且优于已应用的HNIW, 有望成为新型的HEDC.     

The C–H bond dissociation enthalpies in fused N-heterocyclic compounds

The C–H bond dissociation enthalpies (BDEs) of the 26 N, O, S-containing mono-heterocyclic compounds were evaluated using the composite high-level ab initio methods G3 and G4. The C–H BDEs for 32 heterocyclic compounds were calculated using 8 types of density functional theory (DFT) methods. Comparing with the experimental values, the BMK method gave the lowest root mean square error (RMSE) of 7.2 kJ/mol. Therefore, the C–H BDEs of N-fused-heterocyclic compounds at different positions were investigated by the BMK method. By NBO analysis two linear relationships between the C–H BDEs of quinoline and isoquinoline with natural charges qC/e in molecules and with natural charges qC/e in radicals were found. The substituent effects on C_(α)–H BDEs in N-fused-heterocyclic compounds were also discussed. It was found that there are two linear relationships between the C_(α)–H BDEs of quinoline and isoquinoline derivatives with natural charges qC_(α)/e for the EDGs and CEGs substituents.     

A DFT study of cage compounds: 3, 5, 8, 10, 11, 12-hexanitro-3, 5, 8, 10, 11, 12-hexaazatetracyclo [5.5.1.12,6.04,9] dodecane and its derivatives as high energetic materials

A new cage compound, 3, 5, 8, 10, 11, 12-hexanitro-3, 5, 8, 10, 11, 12-hexaazatetracyclo [5.5.1.1^2,6.0^4,9] dodecane (HNHATCD, I) as well as its –ONO₂ (II) and –N₃ (III) derivatives were proposed in the present work. Their molecular structures were optimized at the B3LYP/6-31G(d,p) level of density functional theory. Heat of formation, strain energy, detonation performance, and thermal stability were studied. Results show that the –N₃ group greatly increases the heat of formation, but decreases the strain energy and density, and it is much more helpful for enhancing the detonation energy than the –NO₂ and –ONO₂ groups. An analysis of bond dissociation energies (BDEs) of the weakest bonds implies that the BDE of –N₃ derivatives is the smallest but it is still larger than 120 kJ mol^?1, revealing that these designed compounds have a high thermal stability. Considering the detonation performance and thermal stability, I and II may be potential candidates of high energy density materials.     

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

The nitro derivatives of phenols are optimized to obtain their molecular geometries and electronic structures at the DFT‐B3LYP/6‐31G* level. Detonation properties are evaluated using the modified Kamlet–Jacobs equations based on the calculated densities and heats of formation. It is found that there are good linear relationships between density, detonation velocity, detonation pressure, and the number of nitro and hydroxy groups. Thermal stability and pyrolysis mechanism of the title compounds are investigated by calculating the bond dissociation energies (BDEs) at the unrestricted B3LYP/6‐31G* level. The activation energies of H‐transfer reaction is smaller than the BDEs of all bonds and this illustrates that the pyrolysis of the title compounds may be started from breaking O? H bond followed by the isomerization reaction of H transfer. Moreover, the C? NO₂ bond with the smaller bond overlap population and the smaller BDE will also overlap may be before homolysis. According to the quantitative standard of energetics and stability as a high‐energy density compound, pentanitrophenol essentially satisfies this requirement. In addition, we have discussed the effect of the nitro and hydroxy groups on the static electronic structural parameters and the kinetic parameter. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Theoretical studies on four-membered ring compounds with NF2, ONO2, N3, and NO2 groups

Density functional theory (DFT) method has been employed to study the geometric and electronic structures of a series of four-membered ring compounds at the B3LYP/6-311G** and the B3P86/6-311G** levels. In the isodesmic reactions designed for the computation of heats of formation (HOFs), 3,3-dimethyl-oxetane, azetidine, and cyclobutane were chosen as reference compounds. The HOFs for N(3) substituted derivations are larger than those of oxetane compounds with --ONO2 and/or --NF2 substituent groups. The HOFs for oxetane with --ONO2 and/or --NF2 substituent groups are negative, while the HOFs for N3 substituted derivations are positive. For azetidine compounds, the substituent groups within the azetidine ring affect the HOFs, which increase as the difluoroamino group being replaced by the nitro group. The magnitudes of intramolecular group interactions were predicted through the disproportionation energies. The strain energy (SE) for the title compounds has been calculated using homodesmotic reactions. For azetidine compounds, the NF2 group connecting N atom in the ring decrease the SE of title compounds. Thermal stability were evaluated via bond dissociation energies (BDE) at the UB3LYP/6-311G** level. For the oxetane compounds, the O--NO2 bond is easier to break than that of the ring C--C bond. For the azetidine and cyclobutane compounds, the homolyses of C--NX2 and/or N--NX2 (X = O, F) bonds are primary step for bond dissociation. Detonation properties of the title compounds were evaluated by using the Kamlet-Jacobs equation based on the calculated densities and HOFs. It is found that 1,1-dinitro-3,3-bis(difluoroamino)-cyclobutane, with predicted density of ca. 1.9 g/cm(3), detonation velocity (D) over 9 km/s, and detonation pressure (P) of 41 GPa that are lager than those of TNAZ, is expected to be a novel candidate of high energy density materials (HEDMs). The detonation data of nitro-BDFAA and TNCB are also close to the requirements for HEDMs.     

Apical versus equatorial disposition of substituents in tetraoxyphosphoranes bearing a 1,3,2-dioxaphosphocin ring: implications on apicophilicity in trigonal bipyramidal phosphorus

New spirocyclic (amino/amido)tetraoxyphosphoranes CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P(NRR')(O(2)C(6)Cl(4)) [R = Me, R' = Ph (1), R = R' = i-Pr (2); R = R' = H (3); R = H, R' = Ph (4)] and the isothiocyanatotetraoxyphosphorane CH(2)(6-t-Bu-4-Me-C(6)H(2)O)(2)P(NCS)(O(2)C(6)Cl(4)) (5) have been synthesized. X-ray crystallography for these compounds reveals that -N(Me)Ph, -N(i-Pr)(2), and -NCS groups occupy an apical position whereas -NH(2) and -NHPh groups occupy an equatorial position in a trigonal bipyramidal geometry around phosphorus. These results are in contrast with the common assumption that a sterically bulky and less electronegative substituent [e.g. -N(i-Pr)(2)] should be less apicophilic than a sterically small and more electronegative substituent (e.g. -NH(2)). The possible rationalization for these results is discussed. Variable-temperature ((1)H, (31)P) NMR spectra of these compounds show some unusual features not reported before for pentacoordinate phosphorus. Probable intramolecular processes involving (i) apical-equatorial <--> equatorial-apical exchange, (ii) apical-equatorial <--> equatorial-equatorial exchange, and (iii) boat-chair <--> tub (for the eight-membered ring) interconversion as well as cessation of the P-N bond rotation have been invoked to explain the spectral features.     

Electron ionization mass spectra and tautomerism of 2-phenacylpyridines

The electron ionization mass spectra of 2-phenacylpyridine (ketimine form) and its 13 derivatives substituted in the benzene ring (1an: a R = H, b 3-Me, c 4-Me, d 4-NH(2), e 3-F, f 4-F, g 4-OMe, h 4-Cl,i 4-N(CH(3))(2),j 4-NO(2), k 4-CF(3), l 4-N(CH(2))(4), m 4- Br, n 3-Br) were recorded at 70 eV to determine the fragmentation routes and to screen the presence of their enolimine tautomers, (Z-)-2-(2-hydroxy-2-phenylvinyl)pyridines in the gas phase. The total ion currents (TIC) of the ions [MH](+), [MHCO](+), 2-PyCH(2)O(+), and RC(6)H(4)CO(+) (= ArCO(+) ) showed a fair or good correlation with the Hammett s constants (R = 0.859, 0.876, 0.912, and 0.926, respectively). The relative abundances (RA) of both the [MCO](+.) and the [MHCO](+) ion increased with the decreasing electron donating ability of the substituents and also correlated relatively well with the Hammett constants (R = 0.834 and 0.907, respectively). These observations, in comparison to the NMR results, show that the relative contribution of the ketimine tautomer also increases in the gas phase with the increasing electron donating ability of the phenyl substituent, i.e. the TIC of the ArCO(+) ion decreases whereas that of [MH](+) ion increases.     

多硝基六氮杂金刚烷结构和相对稳定性的理论研究

The density function theory at the B3LYP/6-31G* level was employed to study the structures, including the total energies (EZPE), the geometries, the oxygen balances (OB100), the dipole moments, of polynitrohexaazaadamantanes (PNHAAs) and the potential candidates of high energy density compounds (HEDCs).The structural parameters of PNHAAs, such as the the maximum N-NO2 bond length (LBmax), the least N-N Mulliken population (BN-N), the least negative charge on the nitro group (QNO2) and OB100, were studied to predict their relative stability or sensitivity (the easiness for initiating a detonation, high sensitivity means low stability). It was found that the same conclusion was drawn from the four parameters.With the number of nitro groups increasing, the stabilities of these compounds decrease. OB100 failed in identifying the isomers, but the EZPE energy and the dipole moment were considered to give more reliable results for the isomers.     

Computational Design of High Energy RDX-Based Derivatives: Property Prediction,Intermolecular Interactions,and Decomposition Mechanisms

A series of new high-energy insensitive compounds were designed based on 1,3,5-trinitro-1,3,5-triazinane (RDX) skeleton through incorporating -N(NO₂)-CH₂-N(NO₂)-, -N(NH₂)-, -N(NO₂)-, and -O- linkages. Then, their electronic structures, heats of formation, detonation properties, and impact sensitivities were analyzed and predicted using DFT. The types of intermolecular interactions between their bimolecular assemble were analyzed. The thermal decomposition of one compound with excellent performance was studied through ab initio molecular dynamics simulations. All the designed compounds exhibit excellent detonation properties superior to 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), and lower impact sensitivity than CL-20. Thus, they may be viewed as promising candidates for high energy density compounds. Overall, our design strategy that the construction of bicyclic or cage compounds based on the RDX framework through incorporating the intermolecular linkages is very beneficial for developing novel energetic compounds with excellent detonation performance and low sensitivity.