Thermal behavior of 1,1-diamino-2,2-dinitroethylene

The thermal behavior of 1,1-diamino-2,2-dinitroethlene (DADNE) was followed by differential scanning calorimetry (DSC) and thermogravimetry (TG). In addition, it was further investigated by the combination techniques of in situ thermolysis cell or fast thermolysis probe with rapid-scan Fourier transform infrared spectroscopy (thermolysis/RSFT-IR and fast thermolysis/RSFT-IR) and by mass spectroscopy (MS). The results showed that there was a phase transition (beta-DADNE to gamma-DADNE) at the temperature of 119 degrees C, and that the gas products of DADNE consisted of CO2, CO, NO2, NO, N2O, HCN, and HNCO, of which CO2, NO, N2O, and HCN present themselves in both the first and second stages of DADNE decomposition process, whereas CO, NO2, and HNCO are only caused by the second stage, in air atmosphere. The C=C and C-NH2 bonds of DADNE molecules are broken in the first stage of the decomposition process in open air, and one of the C-NO2 and one of the C-NH2 bonds of the molecules are broken in the same stage under electrospray ionization condition.     

1,1-二氨基-2,2-二硝基乙烯的合成和表征

三氨基三硝基苯(1,3,5-triamino-2,4,6-trinitrobenzene,TATB)非常钝感,已得到广泛应用,但其爆轰能量太低,只相当于奥克托今(1,3．5．7-tetranitro-1,3,5,7-tetrazacyclooctane,HMX)的65％,影响武器的小型化,因此,有必要研究开发新的能量更高的低(钝)感炸药。1,1-二氨基．2,2-二硝基     

Reactions of 1,1-diamino-2,2-dinitroethylene with diamines

Reactions of 1,1-diamino-2,2-dinitroethylene with diamines were studied.     

Coupling effects of high temperature and pressure on the decomposition mechanisms of 1,1-diamino-2,2-dinitroehethe crystal: Ab initio molecular dynamics simulations

Recently, Dreger et al. experimentally investigated the phase diagram and decomposition of 1,1-diamino-2,2-dinitroethene (FOX-7) single crystal compressed hydrostatically up to 10 GPa and heated over a range of 293–750 K (J. Phys. Chem. C 2016 , 120, 11092–11098). As a continuation, we performed ab initio molecular dynamic simulations to study the initiation mechanisms and subsequent decomposition of FOX-7 at a temperature of 504 K (initial decomposition temperature) coupled with a pressure of 1–5 GPa, 604 K at 5GPa, and 704 K at 5 GPa. However, our two compressing ways are different: the former is static hydrostatical compression, while our way is dynamic compression. Our results indicate that the initial decomposition mechanism was dependent on the temperature but independent of the pressure. The initial decomposition step is the bimolecular intermolecular hydrogen transfer. The subsequent decomposition of FOX-7 is sensitive to both the temperature and pressure. At 504 K, the decomposition of FOX-7 was accelerated from 1 to 2 GPa and from 3 to 5 GPa but decelerated from 2 to 3 GPa. The temperature exhibits a positive effect on the decomposition. Overall, the temperature and pressure have great cooperative effects on the decomposition of FOX-7. Our study may provide new insight into understanding the initial mechanisms and decomposition reactions of energetic materials at relatively low temperatures coupled with different pressures in atomic detail.     

Synthesis and characterization of a new cadmium complex based on 1,1-diamino-2,2-dinitroethylene

A new cadmium complex of 1,1-diamino-2,2-dinitroethylene (FOX-7) was synthesized and structurally determined. Central Cd²⁺ is coordinated by six nitrogens from four NH₃ molecules and two FOX-7^? anions to form an octahedral structure. The thermal decomposition of Cd(NH₃)₄(FOX-7)₂ was studied with differential scanning calorimeter and TG–DTG methods. The apparent activation energy and pre-exponential constant of the exothermic process are 220.6 kJ M^?1 and 10^17.86 s^?1, respectively. Cd(NH₃)₄(FOX-7)₂ is sensitive.     

Effect of charged and excited states on the decomposition of 1,1-diamino-2,2-dinitroethylene molecules

The authors have calculated the electronic structure of individual 1,1-diamino-2,2-dinitroethylene molecules (FOX-7) in the gas phase by means of density functional theory with the hybrid B3LYP functional and 6-31+G(d,p) basis set and considered their dissociation pathways. Positively and negatively charged states as well as the lowest excited states of the molecule were simulated. They found that charging and excitation can not only reduce the activation barriers for decomposition reactions but also change the dominating chemistry from endo- to exothermic type. In particular, they found that there are two competing primary initiation mechanisms of FOX-7 decomposition: C-NO2 bond fission and C-NO2 to CONO isomerization. Electronic excitation or charging of FOX-7 disfavors CONO formation and, thus, terminates this channel of decomposition. However, if CONO is formed from the neutral FOX-7 molecule, charge trapping and/or excitation results in spontaneous splitting of an NO group accompanied by the energy release. Intramolecular hydrogen transfer is found to be a rare event in FOX-7 unless free electrons are available in the vicinity of the molecule, in which case HONO formation is a feasible exothermic reaction with a relatively low energy barrier. The effect of charged and excited states on other possible reactions is also studied. Implications of the obtained results to FOX-7 decomposition in condensed state are discussed.     

1,1-二氨基-2,2-二硝基乙烯的合成与性能研究

以2-甲基嘧啶-4,6-二酮为原料, 通过硝化和水解过程合成出FOX-7 (1,1-二氨基-2,2-二硝基乙烯), 经IR, MS, NMR和元素分析鉴定了其结构, 并对影响得率的主要因素进行了简要分析. 重结晶提纯后培养合成产物的单晶, 用四圆衍射仪对其进行了结构解析, 得到了合成产物的晶体学数据. 测试了FOX-7的电火花感度和落锤感度, 并同RDX (1,3,5-三硝基-1,3,5-三氮杂环己烷)、HMX(环四甲撑四硝胺)以及TATB(三氨基三硝基苯)进行了对比, 结果表明FOX-7的感度要低于RDX, 但较TATB差. 同时对原始样品和重结晶FOX-7的外观形貌和热性质进行了测试, 并对变化情况进行了说明, 发现FOX-7的外观形貌和热性质可以进一步改善和优化.     

1,1-二氨基-2,2-二硝基乙烯的合成研究进展

1,1-二氨基-2,2-二硝基乙烯（FOX-7）是一种低感度高能量的新型含能材料.现有的1,1-二氨基-2,2-二硝基乙烯的合成包括以2-甲基咪唑、盐酸乙脒与乙二酸二乙酯、2-甲基-4,6-二羟基嘧啶为前体的三条合成路线.使用硫酸/硝酸体系硝化2-甲基-4,6-二羟基嘧啶可得到2-二硝基亚甲基-5,5-二硝基嘧啶-4,6-二酮,然后水解可得到FOX-7,正相硅胶薄层色谱可对该反应进行监测.使用曲拉通X-100/正己烷体系的反相微乳法可制备FOX-7球形纳米晶;FOX-7球形纳米晶具有良好的应用前景,对其合成工艺与路线进行探索和研究具有一定的意义.     

Ab initio study of the ground state properties of molecular oxygen

The electric and magnetic properties of the ground state of oxygen molecule are calculated by multiconfiguration self-consisted field (MCSCF) method and compared with experimental data: the quadrupole moment, polarizability, the 17O nuclear quadrupole coupling constant, magnetizability tensor, nuclear spin-rotation coupling constant and rotational g factor. The last two constants are calculated for all possible isotope modifications. The rotational, ESR and NMR spectra are discussed. Fermi-contact hyperfine coupling parameter is additionally estimated by different methods. The NMR chemical shielding tensor for 17O16O species at high temperature limit (without electron spin contribution) is predicted. Potential energy curves for 10 excited bound states and the internuclear distance dependence of the studied properties are also presented.     

1,1-二氨基-2,2-二硝基乙烯的比热容、热力学性质及绝热至爆时间研究

应用Micro-DSCⅢ微热量仪的两种连续比热容测定模式对1,1-二氨基-2,2-二硝基乙烯(FOX-7)比热容进行了测定. 得到298.15 K时FOX-7的标准摩尔比热容分别为176.56和176.02 J•mol^－1•K^－1, 相对偏差为0.31%. 运用Gaussian 03W程序的DFT-RB3LYP/6-311＋＋G**方法对FOX-7在283～353 K温度范围内进行了比热容理论计算, 结果为147.11～170.54 J•mol^－1•K^－1, 与Micro-DSCⅢ微热量仪测定值偏差在13.27%～15.46%之间. 用测得的比热容方程计算了298.15 K为基础的FOX-7的热力学函数并得到了绝热至爆时间.     

Ab initio and molecular mechanics study of n-phenyl phthalimide and its crystal structure

Ab initio molecular orbital calculations are reported on the energetics for torsional motion of N-phenyl phthalimide using 3-21G, 6-31G, and 6-31G^** basis sets and incorporating electron correlation effects for selected geometries. With the largest basis set, a minimum energy is found for a torsion angle of 59.2°. Atomic charges are assigned to the molecules on the basis of a least-squares fit to the molecular electrostatic potential. This information is then used in molecular mechanics calculations of the crystal structure, where the calculated unit cell parameters are in good agreement with those observed experimentally.     

The reactivity of 1,1-diamino-2,2-dinitroethene (FOX-7)

The reactivity of 1,1-diamino-2,2-dinitroethene (DADNE) or FOX-7 was studied. Various reactions like cycloadditions, nitration, halogenation and acylation were performed in order to evaluate the reactivity of the C-C double bond and the amino moieties. Several products were isolated and two of them were characterised by X-ray analysis. Two reactive sites were identified. The chemical behaviour of DADNE is also discussed.     

Ab initio study of anomeric effect in 2,2-difluoroglycine

The optimized molecular structures of seven conformations of 2,2-difluoroglycine have been obtained from ab initio calculations. For conformers in which the lone pair of electrons on the nitrogen are antiperiplanar to one of the C–F bonds, that C–F bond is longer than the other C–F bond, which is synperiplanar to the lone pair of electrons. Conformers which have these features are the most stable conformers of those examined. This observation is explained in terms of an anomeric effect of the 1p(N)→σ^*(C–F). At the MP2/6-31G^* level of calculation, conformers IV and V are 21.5 and 18.7 kJ/mol, respectively, more stable than the least stable conformer, VI, which does not exhibit an anomeric effect. Conformer VII was found to be exceptionally stable, in addition to an anomeric effect, this conformer also exhibits features of a FH–O hydrogen bond.     

Ab initio study of organic mixed valency

A series of six radical cations of the type (D L D)⁺ was investigated at the ab initio unrestricted Hartree–Fock level. One localized and one delocalized conformation were systematically searched by full geometry optimization. At both nuclear arrangements, mostly found as being minima in the symmetry‐restrained Hartree–Fock framework, excitation energies were calculated through the expansion of the wave function on single electronic excitations of the Hartree–Fock fundamental determinant and at the unrestricted Hartree–Fock or at the multiconfigurational self consistent field levels. Few calculations were also performed by taking into account some part of the electronic correlation. Except for N,N,N′,N′‐tetramethyl p‐phenylenediamine, all the studied compounds are localized stable cations, at the symmetry‐restrained Hartree–Fock level. However, the reoptimization of their wave function changes this observation since only three of them seem to conserve a localized stable conformation. Most of the studied systems are characterized by one or two excited electronic states very close to the fundamental one and should thus present an unresolved broadened first absorption band in the near‐infrared region. These features are in agreement with the available experimental data. Strong Hartree–Fock instabilities are found for the delocalized structure and put in relation with the existence of the large nonadiabatic coupling in this conformational region. The solvent influence is discussed in the Onsager dipolar reaction field framework. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 76: 552–573, 2000     

Ab initio virial equation of state for argon using a new nonadditive three-body potential

An ab initio nonadditive three-body potential for argon has been developed using quantum-chemical calculations at the CCSD(T) and CCSDT levels of theory. Applying this potential together with a recent ab initio pair potential from the literature, the third and fourth to seventh pressure virial coefficients of argon were computed by standard numerical integration and the Mayer-sampling Monte Carlo method, respectively, for a wide temperature range. All calculated virial coefficients were fitted separately as polynomials in temperature. The results for the third virial coefficient agree with values evaluated directly from experimental data and with those computed for other nonadditive three-body potentials. We also redetermined the second and third virial coefficients from the best experimental pρT data utilizing the computed higher virial coefficients as constraints. Thus, a significantly closer agreement of the calculated third virial coefficients with the experimental data was achieved. For different orders of the virial expansion, pρT data have been calculated and compared with results from high quality measurements in the gaseous and supercritical region. The theoretically predicted pressures are within the very small experimental errors of ±0.02% for p ≤ 12 MPa in the supercritical region near room temperature, whereas for subcritical temperatures the deviations increase up to +0.3%. The computed pressure at the critical density and temperature is about 1.3% below the experimental value. At pressures between 200 MPa and 1000 MPa and at 373 K, the calculated values deviate by 1% to 9% from the experimental results.     

Ab initio vs molecular mechanics thermochemistry: homocubanes

The standard enthalpies of formation and strain energies for a series of homocubanes have been investigated by high-level ab initio G3(MP2)/B3LYP method. The relative stabilities of isomers are discussed. The comparison is made between the results of ab initio and molecular mechanics methods with the aim of assessing their performances. The usefulness of high-level calculations for generating thermochemical databases of relatively large molecules (e.g. C(11)H(14)) was also demonstrated.     

Polyiodide chains in crystalline organic iodides: Ab initio Hartree–Fock crystal orbital study

Hartree–Fock crystal orbital calculations of two crystalline organic iodides, tetrathiafulvalenium triiodide (TTF∗︁I₃) and dipyridinium decaiodide (NHC₅H₅)₂∗︁I₁₀, were carried out. The former crystal contains no true polyiodide chains, whereas such chains are present in the latter crystal. In such a way, the effect of the polyiodide chain formation on the electronic structure of crystalline organic iodides was studied. The present calculations show that crystalline organic iodides with polyiodide chains could, in principle, be quasi-one-dimensional semiconductors. A polyiodide chain could be a carrier of semiconductivity only when it is formed by fully charged iodide anions (no charge transfer from the chain). © 1997 John Wiley & Sons, Inc. Int J Quant Chem 64 : 473–479, 1997