硝酸酯的热分解性能

分别在B3LYP/6-31G*和MP2/6-31G*的理论水平下,计算得到硝酸正丙酯、硝酸异丙酯、硝酸异辛酯和二缩三乙二醇二硝酸酯4种硝酸酯的O-NO2键离解能(BDE)。 采用常压DSC和高压DSC实验方法,研究了4种硝酸酯的热分解过程,获得热分解反应动力学参数。 常压下4种物质的热分解反应发生在气相区,当压力增大至2 MPa时,4种物质直接发生液相分解反应。 4种硝酸酯的O-NO2键离解能在很大程度上符合由实验分析得到的活化能,表明4种硝酸酯的热分解反应只是单分子O-NO2键的均裂反应。     

A theoretical study of five nitrates: Electronic structure and bond dissociation energies

Three density-functional methods (B3P86, B3PW91, and B3LYP) are employed to investigate the O–NO₂ bond lengths, frontier orbital energies, and O–NO₂ bond dissociation energies (BDEs) of n-propyl nitrate (NPN), isopropyl nitrate (IPN), 2-ethylhexyl nitrate (EHN), triethylene glycol dinitrate (Tri-EGDN), and tetraethylene glycol dinitrate (Tetra-EGDN). It is found that the O–NO₂ bond lengthens (destabilizes) in the order of IPN, NPN, EHN, Tetra-EGDN, and Tri-EGDN. From the data of frontier orbital energies (E_HOMO, E_LUMO), and energy gaps (ΔE), we estimate the relative thermal stability ordering of five nitrates and their corresponding radicals. The predicted BDEs of O–NO₂ bond in NPN, IPN, EHN, Tri-EGDN, and Tetra-EGDN, are 176.6, 174.5, 168.1, 156.1, and 159.3 kJ mol⁻¹, respectively. Based on the finding that the present results of BDEs are well coincident with the experimental results of apparent activation energies from the literature, we can draw a conclusion that the experimental thermolysis of five nitrates is only unimolecular homolytical cleavage of the O–NO₂ bonds.     

A theoretical study of explosive sensitizers

Quantum chemical calculations at the HF/6-31G^* and B3LYP/6-31G^* levels have been performed on five explosive sensitizers, ethyl nitrate (EN), n-propyl nitrate (NPN), isopropyl nitrate (IPN), 2-ethylhexyl nitrate (EHN) and tetraethylene glycol dinitrate (TEGDN). Theoretical study has made a detailed molecular-level investigation of the title compounds. Based on the Mulliken populations and bond lengths, the fission of the O₂–N₃ can be acceptable reasonably. Charge distribution analysis indicates that the five nitrates produce NO₂ gas during the dissociation of the O₂–N₃ weak bond. We also order the relative thermal stability of five nitrates on the basis of frontier orbital energy (E _HOMO, E _LUMO) and energy gap (ΔE = E _HOMO − E _LUMO).     

炸药敏化剂的分子结构、电子结构和生成热的理论研究

在HF/6-31G*和B3LYP/6-31G*基组水平上, 对硝酸乙酯(EN)、硝酸正丙酯(NPN)、硝酸异丙酯(IPN)、硝酸异辛酯(EHN)和四甘醇二硝酸酯(TEGDN)五种炸药敏化剂进行理论计算, 研究了标题物的分子结构、电子结构和能量等方面的性质. 基于Mulliken布居和键长分析, 五种硝酸酯分子的热分解始于O2—N3键的断裂, 且由Mulliken电荷分布推知分子热解产生NO2气体. 在分析前线轨道能(EHOMO, ELUMO)和能量差(ΔE)的基础上对五种硝酸酯的相对热稳定性大小进行了评估. 由等键反应获得的EN、IPN、NPN、EHN和TEGDN的标准生成热分别是-155.972、-190.896、-175.279、-272.376和-790.733 kJ·mol-1.     

Theoretical Studies on the Structures,Thermodynamic Properties,Detonation Performance,and Pyrolysis Mechanisms for Six Dinitrate Esters

Density functional theory (DFT) has been employed to study the geometric and electronic structures of six dinitrate esters including ethylene glycol dinitrate (EGDN), diethylene glycol dinitrate (Di‐EGDN), triethylene glycol dinitrate (Tri‐EGDN), tetraethylene glycol dinitrate (Tetra‐EGDN), pentaethylene glycol dinitrate (Penta‐EGDN) and hexaethylene glycol dinitrate (Hexa‐EGDN) at the B3LYP/6‐31G* level. Their IR spectra were obtained and assigned by vibrational analysis. Based on the frequencies scaled by 0.96 and the principle of statistic thermodynamics, the thermodynamic properties were evaluated, which were linearly related with the number of CH₂CH₂O groups as well as the temperature, obviously showing good group additivity. Detonation performances were evaluated by the Kamlet‐Jacobs equations based on the calculated densities and heats of formation. It was found that density, detonation velocity, detonation pressure decreased with the increase of the number of CH₂CH₂O groups. Thermal stability and the pyrolysis mechanism of the title compounds were investigated by calculating the bond dissociation energies (BDE) at the B3LYP/6‐31G* level. For the nitrate esters, the O‐NO₂ bond is a trigger bond during a thermolysis initiation process.     

Theoretical studies on new potential high energy density compounds (HEDCs) adamantyl nitrates from gas to solid

A series of adamantyl nitrates have been theoretically studied from gas to solid to search for new po-tential high energy density compounds (HEDCs). The heats of formation (HOFs) for the 26 title com-pounds were calculated by designing isodesmic reactions at the B3LYP/6-31G level. It was found that the HOFs of the 26 isomers with the same number of —ONO2 groups (n) are not correlated well with the corresponding substituted positions. According to the obtained heats of detonation (Q),detonation velocities (D),and detonation pressures (P) using the Kamlet-Jacobs equations,it was found that when n=7～8,the adamantyl nitrates meet the criterion as an HEDC. The calculations on bond dissociation energies of O—N (EO—N) showed that the adamantyl nitrates with gemi —ONO2 always have the worst stability among the isomers,and all the adamantyl nitrates with gemi —ONO2 have similar stability. Due to the complexity of their structures,values of EO—N do not decrease with the increase of the substituent number n obviously,and the stability of adamantyl nitrates is not determined by only one structural parameter. Considering the stability requirement,only 1,2,4,6,8,9,10-adamantyl heptanitrate is recom-mended as a feasible HEDC. Molecular packing searching for 1,2,4,6,8,9,10-adamantyl heptanitrate among 7 most possible space groups (P21/c,P-1,P212121,P21,Pbca,C2/c,and Pna21) using Compass and Dreiding force fields showed that this compound tends to crystallize in P21/c. Ab initio periodic calculations on the electronic structure of the predicted packing showed that the O—NO2 bond is the trigger bond during thermolysis,which agrees with the result derived from the study of dissociation energies of O—N bonds.     

反式-1,4,5,8-四硝基-1,4,5,8-四氮杂萘烷异构体热解机理与稳定性的理论研究

运用密度泛函理论和半经验分子轨道方法,对一系列高能杂环硝胺—反式-1,4,5,8-四硝基-1,4,5,8-四氮杂萘烷异构体的热解机理和稳定性进行了系统地计算研究。在B3LYP/6-31G**和PM3水平上,分别计算了标题物的化学键离解能(BDE)和热解反应活化能(Ea),并根据BDE和Ea数值考察了硝胺取代基对化合物稳定性和热解机理的影响;同时,还详细考察了BDE与Ea、化学键重叠布居数、前线轨道能级以及能隙之间的相关性。结果表明,由BDE、Ea和静态电子结构参数推断的标题物热稳定性和热解机理的结论基本是一致的,N-NO2键均裂是标题物的热解引发步骤,间位取代异构体较对位取代异构体稳定,而邻位取代的异构体稳定性最差。     

Gas-phase thermal decomposition of peroxy-N-butyryl nitrate

The gas-phase thermal decomposition rate of peroxy-n-butyryl nitrate (n-C₃H₇C(O)OONO₂, PnBN) has been measured at ambient temperature (296 K) and 1 atm of air relative to that of peroxyacetyl nitrate (CH₃C(O)OONO₂, PAN) using mixtures of PAN (14–19 ppb), PnBN (22–46 ppb), and nitric oxide (1.35–1.90 ppm). The PnBN/PAN decomposition rate ratio was 0.773 ± 0.030. This ratio, together with a literature value of 3.0 × 10^?4 s^?1 for the thermal decomposition rate of PAN at 296 K, yields a PnBN thermal decomposition rate of (2.32 ± 0.09) × 10^?4 s^?1. The results are briefly discussed by comparison with data for other peroxyacyl nitrates and with respect to the atmospheric persistence of PnBN. © 1994 John Wiley & Sons, Inc.     

Kinetic Study and NBO Analysis of the Dehydrogenation Mechanism of Five‐membered Ring Heterocyclic 2,5‐Dihydro‐[furan,thiophene, selenophene

The theoretical study of the dehydrogenation of 2,5‐dihydro‐[furan ( 1 ), thiophene ( 2 ), and selenophene ( 3 )] was carried out using ab initio molecular orbital (MO) and density functional theory (DFT) methods at the B3LYP/6‐311G**//B3LYP/6‐311G** and MP2/6‐311G**//B3LYP/6‐311G** levels of theory. Among the used methods in this study, the obtained results show that B3LYP/6‐311G** method is in good agreement with the available experimental values. Based on the optimized ground state geometries using B3LYP/6‐311G** method, the natural bond orbital (NBO) analysis of donor‐acceptor (bond‐antibond) interactions revealed that the stabilization energies associated with the electronic delocalization from non‐bonding lone‐pair orbitals [LP(e)_X3] to δ*_{C(1)  H(2)} antibonding orbital, decrease from compounds 1 to 3 . The LP(e)_X3→δ*_{C(1)  H(2)} resonance energies for compounds 1 – 3 are 23.37, 16.05 and 12.46 kJ/mol, respectively. Also, the LP(e)_X3→δ*_{C(1)  H(2)} delocalizations could fairly explain the decrease of occupancies of LP(e)_X3 non‐bonding orbitals in ring of compounds 1 – 3 ( 3 > 2 > 1 ). The electronic delocalization from LP(e)_X3 non‐bonding orbitals to δ*_{C(1)  H(2)} antibonding orbital increases the ground state structure stability, Therefore, the decrease of LP(e)_X3→δ*_{C(1)  H(2)} delocalizations could fairly explain the kinetic of the dehydrogenation reactions of compounds 1 – 3 (k ₁ >k ₂ >k ₃ ). Also, the donor‐acceptor interactions, as obtained from NBO analysis, revealed that the (_C(4)C(7)→δ*_{C(1)  H(2)} resonance energies decrease from compounds 1 to 3 . Further, the results showed that the energy gaps between (_C(4)C(7) bonding and δ*_{C(1)  H(2)} antibonding orbitals decrease from compounds 1 to 3 . The results suggest also that in compounds 1 – 3 , the hydrogen eliminations are controlled by LP(e)→δ* resonance energies. Analysis of bond order, natural bond orbital charges, bond indexes, synchronicity parameters, and IRC calculations indicate that these reactions are occurring through a concerted and synchronous six‐membered cyclic transition state type of mechanism.     

Lanthanide nitrate complexes with 2-azacyclononanone

Thermal behavior of rare earth nitrate complexes with 2-azacyclononanone (AZA) with Ln(NO₃)₃·3(AZA) composition (where Ln=Gd, Er and Ho) was analyzed in kinetic point of view. Kinetic parameters were calculated from thermogravimetric data. All obtained results were similar. The first decomposition step was representative to the loss of ligand and the residue was essentially Ln₂O₃. Furthermore, a reaction path was proposed for the thermal decomposition of the Ln(NO₃)₃·3(AZA).     

Catalytic effect investigation of α-Fe2O3 and α-Fe2O3-CMS nanocomposites on the thermal behavior of NC/DEGDN mixture: DSC measurements and kinetic modeling

In this work, the thermal behavior and kinetics of energetic systems containing α-Fe₂O₃ and iron oxide–carbon mesospheres (α-Fe₂O₃-CMS) with nitrocellulose (NC)/diethylene glycol dinitrate (DEGDN)-based composites have been investigated using differential scanning calorimetry DSC and four isoconversional kinetic methods, respectively. The obtained results indicate that NC/DEGDN show only one decomposition peak, corresponding to the decomposition of the nitrate esters. Furthermore, the introduction of α-Fe₂O₃ and α-Fe₂O₃-CMS have lowered the peak temperature by 3.1 °C and 4.7 °C, respectively. Besides, the activation energy of the thermal decomposition of NC/DEGDN was decreased by 11.9 kJ/mol and 27.97 kJ/mol, after the introduction of α-Fe₂O₃ NPs and α-Fe₂O₃ NPs supported on CMS. These results confirm the good catalytic effect of the added catalysts on the thermal decomposition of the NC/DEGDN mixtures. However, the best catalytic effect was provided by the α-Fe₂O₃-CMS. Furthermore, the three considered systems were found to decompose according to different integral models g(α).     

硝酸酯分子几何构型的量子化学研究

运用MINDO / 3、MNDO 和AM1 三种半经验分子轨道(MO)方法, 通过SCF计算, 首次系统地获得了32个硝酸酯化合物分子的全优化几何构型。三种方法的计算结果与已报道的四个化合物(硝酸甲酯、吉纳、硝化甘油和太安)的实验结果相比, AM1法较好。所有硝酸酯的酯基(-ONO~2)具有近似不变的几何参数。直链烷基硝酸酯的键长和键角极为相近, 全部重原子均共平面。二元直链和四元硝酸酯具有对称的分子构型。     

Evaluation of the thermal oxidative stability of polyimides via TGA techniques

Thermogravimetric analysis (TGA) has been used for many years to evaluate polymer thermal stability. The objective of this study is to determine if weight-loss curves from TGA and isothermal TGA (IGA) can be used to determine degradation activation energies and thus rank the thermal stability (TS) and thermooxidative stability (TOS) for selected polyimides. Two high-temperature stable addition-cured polyimides and two aromatic condensation polyimides, all four containing fluorinated connecting linkages in the dianhydride monomers, were compared. Three TGA kinetic methods (Coats/Redfern, Ingraham/Marier, Horowitz/Metzger) were used to determine the activation energy for decomposition in air. The results were then used to rank polyimide stability compared to more traditional rankings based on long-term isothermal air aging weight-loss (IWL) studies and thermal decomposition temperatures (T_d) from TGA data. Use of TGA coupled to a Fourier transform infrared (TGA–FTIR) spectrophotometer allowed for the simultaneous identification and relative quantification of evolved decomposition products (CO₂, CO, ArNCO, and CHF₃) of the four polyimides degraded in air or nitrogen. Isothermal TGA–FTIR (IGA–FTIR) was also done in air to determine the relative rate of product evolution at a constant temperature. Activation energies using TGA and IGA data were determined and then compared with IWL values for the degradation of the polyimide to examine for correlations of real-life thermal oxidative aging to accelerated aging techniques. The Coats/Redfern method and T_d were found to best reproduce stability rankings of those from long-term, high-temperature IWL studies. Together, they may provide a time-saving technique to evaluate polyimide thermal oxidative stability. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3943–3956, 1999     

Synthesis and study of organic nitrates of the heterofunctional series

The first representative of organic nitrates of the oxazoline series, 4,4-dihydroxymethyl-2-(3-pyridyl)-2-oxazoline dinitrate, was synthesized by the reaction ofN-nicotinoyltri(hydroxymethyl)aminomethane trinitrate hydronitrate (1) with a solution of KOH in alcohol. The reactivities of compound1 andN-nicotinoylethanolamine nitrate (nicorandil) in the reaction of intramolecular heterocyclization were compared. The structure of the compound synthesized has been established by X-ray diffraction analysis. For Part 1, see Ref. 1 Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 478–481, March, 1998.     

Synthesis and Structure of Tetraphenylantimony Nitrate

The reaction of pentaphenylantimony with triphenylantimony dinitrate in toluene gives tetraphenylantimony nitrate in 99% yield. The X-ray diffraction data show that the antimony atom in the molecule of tetraphenylantimony nitrate has a distorted trigonal-bipyramidal coordination with axial location of the oxygen atom of the nitrate group. The Sb-O, Sb_{a x}, and Sb-C_{e q} bond lengths in two independent molecules of tetraphenylantimony nitrate are 2.498(3), 2.548(2); 2.134(3), 2.138(3); and 2.101(3)-2.112 Å.     

Preparation of New Solid Bases Derived from Supported Metal Nitrates and Carbonates

A highly basic solid catalyst was obtained by dispersing nitrates or carbonates of alkali metals such as KNO₃, CsCO₃ over alumina and zirconia at the surface density of 10-15 × 10¹⁸ cations m^-2 and heating them at 773-873 K in an inert atmosphere. The temperature is far below the decomposition temperatures of the nitrates and the carbonates. Based on the temperature-programmed decomposition (TPD) experiments, two types of decomposition process are suggested; a bulk decomposition and an anion decomposition. Generation of a strong basicity relates to the anion decomposition. The basic center may be composed of the oxygen anions liberated from the decomposition of the nitrate or carbonate anions that are dissociatively adsorbed on the support surface during the preparation. These catalysts effectively catalyzed the double bond isomerization of aliphatic hydrocarbons and bicyclic hydrocarbons at moderate temperature.     

Complexes of (2-methyl-4-oxopent-2-yl)diphenylphosphine oxide with uranyl and neodymium nitrates: synthesis and structures in the solid state and in solution

The reactions of (2-methyl-4-oxopent-2-yl)diphenylphosphine oxide (L) with uranyl and neodymium nitrates afforded complexes with compositions M: L = 1: 2 and 1: 3. These complexes were characterized by X-ray diffraction, IR spectroscopy, and elemental analysis. In the solid complexes, phosphine oxide L has a variable denticity. Studies by ¹H and ³¹P NMR and IR spectroscopy showed that in chloroform, the mononuclear complexes [UO₂(O-L)₂-(O,O-NO₃)₂], [Nd(O-L)₂(O,O-NO₃)₃] and [Nd(O-L)₃(O,O-NO₃)₃] are neutral, and the ligand molecules are coordinated to the metal cation through the phosphoryl oxygen atom.     

Some dn Metal Complexes with 4,4'-bipyridine and Trichloroacetates. Preparation,characterization and thermal properties

The new mixed ligand complexes with formulae Co(4-bpy)₂L₂⋅2H₂O (I), Cu(4-bpy)₂L₂⋅H₂O (II) and Cd(4-bpy)L₂⋅H₂O (III) (4-bpy=4,4'-bipyridine, L=CCl₃COO^–) were prepared. Analysis of the IR spectra indicate that 4-bpy is coordinated with metal ions and carboxylates groups bond as bidentate chelating ligands. The electronic spectra are in accordance with pseudo-octahedral environment around the central metal ion in the Co(II) and Cu(II) complexes. The thermal decomposition of the synthesized complexes was studied in air. A coupled TG-MS system was used to analyse the principal volatile thermal decomposition products of Co(II) and Cu(II) complexes. Corresponding metal oxides were identified as a final product of pyrolysis with intermediate formation of metal chlorides. This revised version was published online in July 2006 with corrections to the Cover Date.     

Negative chemical ionization mass spectrometry of explosives

The negative chemical ionization mass spectra of nitrobenzene, ethylene glycol dinitrate and nitroglycerine have been obtained using various reagent ions. For nitrobenzene, [OH]^? gives the [M ? H]^?, together with [M]^?˙ ions formed by electron capture, but other reagent ions gave relatively low intensity adduct peaks. Ethylene glycol dinitrate and nitroglycerine gave abundant [M + X]^? ions (X = NO₂, NO₃, Cl, Br, I), together with ions arising from the thermal decomposition of the samples in the heated inlet system. The rate of anion attachment to these compounds is much greater than that to related compounds having only one functional group, and it is suggested that this is due to the participation of the adjacent groups in the bonding between the substrate and anion.     

Preparation,characterization and compatibility studies of poly(DFAMO/AMMO)

Poly(3-difluoroaminomethyl-3-methyl oxetane (DFAMO)/3-azidomethyl-3-methyl oxetane (AMMO)) (PDA) can be used as an energetic pre-polymer in the binder systems of solid propellants and polymer-bonded explosives (PBXs). The cationic solution polymerization affords PDA using butane diol (BDO) and boron trifluride etherate (TFBE) as initiator and catalyst, separately. Its molecular structure is characterized and thermal decomposition behavior is investigated by thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The copolymer has good thermal stability and exhibits a three-step mass-loss process with the first two steps mainly belonging to the thermal decomposition of difluoroamino and azido groups, respectively. DSC method is performed to evaluate the compatibility of PDA with some energetic components and inert materials. More than half of the selected materials are compatible with PDA, which including cyclotrimethylenetrinitramine (RDX), 2,4,6-trinitrotoluene (TNT), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), pentaerythritol tetranitrate (PETN), ammonium perchlorate (AP), ammonium nitrate (AN), potassium nitrate (KNO₃), aluminum powder (Al), aluminum oxide (Al₂O₃), 2-nitrodiphenylamine (NDPA) and 1,3-diethyl-1,3-diphenyl urea (C₁).