[Study of the termination of two acrylonitrile radicals and infrared spectrum].

By using the density functional theory, the study of reaction termination mechanism of two (CH3)2 (CN)C--CH2-- (CN)CH was carried out at the B3LYP/6-31G(d) level. The initiator AIBN was used. Reactants, coupled intermediates, transition states and disproportionation products were optimized at the B3LYP/6-31G(d) level. Then the total energies corrected by zero-point energy, vibrational frequencies and electronic structures were calculated, the transition states structure was also verified. The results show that it forms the energy-rich adducts a through the coupling termination. Then, the disproportionation product P[p1 (CH3)2 (CN) C-CH=CHCN + p2 (CH3)2 (CN)C-CH2-CH2CN] formed via hydrogen shift and dissociation. The reactions of coupling termination and disproportionation termination are all exothermic reactions, and the coupled product has lower energy. The rate constant of step a→TS→P k(298.15 K) = 2.71 x 10(-59) at the normal atmospheric temperature. Disproportionation termination occurs more easily with the reaction temperature rising, so the proportion of disproportionation products is increasing. Also, the analysis of infrared spectrogram of each species in reaction process shows chemical change of free radicals in the whole termination reaction. The authors give the HOMO-LUMO in this paper to verify the accuracy of biradical coupling termination and structures. It has important guiding significance to controlling the free radicals termination methods of acrylonitrile monomer.

[Study on preparation of deoxyrhaponti-beta-cyclodextrin super-molecular inclusion complex and performance of inclusion complex].

To prepare beta-cyclodextrin (beta-CD)-deoxyrhaponti inclusion complex by the homogeneous method, and characterize the inclusion complex with ultraviolet-visible spectrum and fluorescence spectroscopy, in order to determine the inclusion rate, the ratio of subject-object, the binding constant of supra-molecular system and the thermodynamic function. The results showed that the designed method was so rational that the inclusion complex was successfully prepared. The ultraviolet-visible spectrophotometry method was adoptedto determine the inclusion rate of 38%, and the ratio of subject-object of 2: 1. The thermodynamic parameters of this inclusion complex: deltaH(0), deltaS(0) was all smaller than zero, which indicated that the main acting forces generated by the inclusion complex were hydrogen bonding and Vander Waals' force. deltaG(0) < 0 and deltaG(0) were directly proportional to the reaction temperature, which suggested that the reaction would spontaneously increase with the temperature rise. The polarization fluorescence method was used to quantitatively prove the non-covalent inclusion complex generated during the interaction between beta-CD interacting with DES. The results could also provide reference for studies on cyclodextrin supra-molecular system.

Density functional theory study of high-pressure effect on crystalline 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine.

Periodic density functional theory calculations are performed to study the hydrostatic compression effects on the structure, electronic, and thermodynamic properties of the energetic polyazide 4,4',6,6'-tetra(azido)hydrazo-1,3,5-triazine (TAHT) in the range of 0-100 GPa. At the ambient pressure, the local density approximation/Ceperley-Alder exchange-correlation potential parameterized by Perdew and Zunger relaxed crystal structure compares well with the experimental results. The predicted heat of sublimation is 38.68 kcal/mol, and the evaluated condensed phase of formation (414.04 kcal/mol) approximates to the experimental value. The detonation velocity and detonation pressure for the solid TAHT are calculated to be 7.44 km/s and 23.71 GPa, respectively. When the pressure is exerted less than 35 GPa, the crystal structure and geometric parameters change slightly. However, at 36 GPa, the molecular structure, band structure, and density of states change abnormally because of the azide-tetrazole transformation that has not been observed in gas phase or polar solvents. The azido group cyclizes to form a five-membered tetrazole ring that is coplanar with the riazine ring and contributes to a larger conjunction system. As the pressure augments further to 80 GPa, the hydrogen transfer is found and a new covalent bond H2-N9 is formed. In the studied pressure range, the band gap decreases generally except for some breaks due to the molecular transformation and drops to nearly zero at 100 GPa, which means the electronic character of the crystal changes toward a metallic system. An analysis of the electronic structure shows that an applied pressure increases the impact sensitivity of TAHT.

Theoretical investigations of a high density cage compound 10-(1-nitro-1, 2, 3, 4-tetraazol-5-yl)) methyl-2, 4, 6, 8, 12-hexanitrohexaazaisowurtzitane.

A new polynitro cage compound with the framework of HNIW and a tetrazole unit, i.e., 10-(1-nitro-1, 2, 3, 4-tetraazol-5-yl)) methyl-2, 4, 6, 8, 12-hexanitrohexaazaisowurtzitane (NTz-HNIW) has been proposed and studied by density functional theory (DFT) and molecular mechanics methods. Properties such as IR spectrum, heat of formation, thermodynamic properties, and crystal structure were predicted. The compound belongs to the Pbca space group, with the lattice parameters a = 15.07 Å, b = 12.56 Å, c = 18.34 Å, Z = 8, and ρ = 1.990 g·cm(-3). The stability of the compound was evaluated by the bond dissociation energies and results showed that the first step of pyrolysis is the rupture of the N-NO(2) bond in the side chain. The detonation properties were estimated by the Kamlet-Jacobs equations based on the calculated crystal density and heat of formation, and the results were 9.240 km·s(-1) for detonation velocity and 40.136 GPa for detonation pressure. The designed compound has high thermal stability and good detonation properties and is probably a promising high energy density compound (HEDC).

A theoretical study on the reaction mechanism of O2 with C4H9• radical.

Ab initio calculations have been performed using the complete basis set model (CBS-QB3) to study the reaction mechanism of butane radical (C(4)H(9)•) with oxygen (O(2)). On the calculated potential energy surface, the addition of O(2) to C(4)H(9)• forms three intermediates barrierlessly, which can undergo subsequent isomerization or decomposition reaction leading to various products: HOO• + C(4)H(8), C(2)H(5)• + CH(2)CHOOH, OH• + C(3)H(7)CHO, OH• + cycle-C(4)H(8)O, CH(3)• + CH(3)CHCHOOH, CH(2)OOH• + C(3)H(6). Five pathways are supposed in this study. After taking into account the reaction barrier and enthalpy, the most possible reaction pathway is C(4)H(9)• + O(2) → IM1 → TS5 → IM3 → TS6 → IM4 → TS7 → OH• + cycle-C(4)H(8)O.

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 [5.5.1.1(3, 11).1 (5, 9)] pentadecane.

A new polynitro cage compound 2, 4, 6, 8, 10, 12, 13, 14, 15-nonanitro-2, 4, 6, 8, 10, 12, 13, 14, 15-nonaazaheptcyclo [5.5.1.1(3,11).1(5,9)] pentadecane (NNNAHP) was designed in the present work. Its molecular structure was optimized at the B3LYP/6-31 G(d,p) level of density functional theory (DFT) and crystal structure was predicted using the Compass and Dreiding force fields and refined by DFT GGA-RPBE method. The obtained crystal structure of NNNAHP belongs to the P-1 space group and the lattice parameters are a = 9.99 Å, b = 10.78 Å, c = 9.99 Å, α = 90.01°, ß = 120.01°, γ = 90.00°, and Z = 2, respectively. Based on the optimized crystal structure, the band gap, density of state, thermodynamic properties, infrared spectrum, strain energy, detonation characteristics, and thermal stability were predicted. Calculation results show that NNNAHP has detonation properties close to those of CL-20 and is a high energy density compound with moderate stability.

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).

DFT studies on a high energy density cage compound 4-trinitroethyl-2,6,8,10,12-pentanitrohezaazaisowurtzitane.

Polynitro cage compound 4-trinitroethyl-2,6,8,10,12-pentanitrohexaazaisowurtzitane has the same framework with but higher stability than CL-20 and is a potential new high energy density compound (HEDC). In this paper, the B3LYP/6-31G(d,p) method of density functional theory (DFT) has been used to study its heat of formation, IR spectrum, and thermodynamic properties. The stability of the compound was evaluated by the bond dissociation energies. The calculated results show that the first step of pyrolysis is the rupture of the N-NO(2) bond in the side chain and verify the experimental observation that the title compound has better stability than CL-20. The crystal structure obtained by molecular mechanics belongs to the P2(1)2(1)2(1) space group, with lattice parameters a = 12.59 Å, b = 10.52 Å, c = 12.89 Å, Z = 4, and ρ = 2.165 g·cm(-3). Both the detonation velocity of 9.767 km·s(-1) and the detonation pressure of 45.191 GPa estimated using the Kamlet-Jacobs equation are better than those of CL-20. Considering that this cage compound has a better detonation performance and stability than CL-20, it may be a superior HEDC.

Theoretical prediction of properties of aliphatic polynitrates.

Aliphatic polynitrates are studied using the density functional theory B3LYP method with basis set 6-31G*. The assigned infrared spectrum is obtained and is used to compute the thermodynamic properties based on the frequencies scaled by 0.96 and the principle of statistic thermodynamics. On comparison of the theoretical densities with the experimental ones, the reliability of this theoretical method is tested. Detonation properties are evaluated using the modified Kamlet-Jacobs equations based on the calculated densities and heats of formation. According to the largest exothermic principle, the relative specific impulse (Is) 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 methylene nitrate group could decrease the specific impulses on whole. Moreover, in combination with the energetic properties, xylitol pentanitrate, mannitol hexanitrate, volemitol heptanitrate, and 1,2,3,4,5,6,7,8-octanitrate n-octane are potential candidates for high energy density 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.