Theoretical study on polynitro imidazo [4, 5-e] oxadiazolo [3, 4-b] pyrazine compounds.

The B3PW91/6-31G** theoretical method was carried out to optimize the structure of 12 polynitro imidazo [4,5-e] oxadiazolo [3,4-b] pyrazine compounds (two structural type). The influence of nitro groups on the structure, oxygen balance, density, heat of formation, detonation performances, and charge were investigated. The results showed that the oxygen balance, density, heat of formation, detonation velocity, detonation pressure, and detonation heat increased with different relationships when the number of nitro groups increased. The contribution of the dinitroethylene group to energy was greater than that of the nitroimino group. On the whole, the sensitivity of all compounds increased with the number of -NO2 groups, and the second type of compound is more sensitive because of more nitro groups. The alkaline of the amine will decrease with the increasing number of -NO2 groups, and nitrification action will become more difficult. Graphical abstract Polynitro imidazo [4, 5-e] oxadiazolo [3, 4-b] pyrazine compoundsᅟ.

Roads to pentazolate anion: a theoretical insight.

The formation mechanism of pentazolate anion (PZA) is not yet clear. In order to present the possible formation pathways of PZA, the potential energy surfaces of phenylpentazole (PPZ), phenylpentazole radical (PPZ-R), phenylpentazole radical anion (PPZ-RA), PPZ and m-chloroperbenzoic acid (m-CPBA), p-pentazolylphenolate anion (p-PZPolA) and m-CPBA, and p-pentazolylphenol (p-PZPol) and m-CPBA were calculated by the computational electronic structure methods including the hybrid density functional, the double hybrid density functional and the coupled-cluster theories. At the thermodynamic point of view, the cleavages of C-N bonds of PPZ and PPZ-R need to absorb large amounts of heat. Thus, they are not feasible entrance for PZA formation at ambient condition. But excitation of PPZ and deprotonation of PPZ-RA probably happen before cleavage of C-N bond of PPZ at high-energy condition. As to the radical anion mechanism, the high accuracy calculations surveyed that the barrier of PZA formation is probably lower than that of dinitrogen evolution, but the small ionization potential of PPZ-RA gives rise to the unstable ionic pair of sodium PPZ at high temperature. In respect of oxidation mechanism, except for PPZ, the reactions of p-PZPolA and p-PZPol with m-CPBA can form PZA and quinone. The PZA formations have the barriers of about 20 kcal mol-1 which compete with the dinitrogen evolutions. The stabilities of PZA in both solid and gas phases were also studied herein. The proton prefers to transfer to pentazolyl group in the (N5)6(H3O)3(NH4)4Cl system which leads to the dissociation of pentazole ring. The ground states of M(N5)2(H2O)4 (M = Co, Fe and Mn) are high-spin states. The pentazolyl groups confined by the crystal waters in the coordinate compounds can improve the kinetic stability. As to the reactivity of PZA, it can be persistently oxidized by m-CPBA to oxo-PZA and 1,3-oxo-PZA with the barriers of about 20 kcal mol-1.

Study on the computer-aided design of high energetic compounds based on the 1,2,3,4-tetrazine-1,3-dioxide frame.

In order to discover more potential high energy compounds, five computer-aided design methods were founded, and 20 high energetic compounds based on the 1,2,3,4-tetrazine-1,3-dioxide frame were designed. The first step of computer-aided design methods was to design new frame M. Three combination rules were invented, they were simple double-points rule, complicated double-points rule, and complicated multi-points rule. The second step of computer-aided design methods was to design 1,2,3,4-tetrazine 1,3-dioxides derivants by connecting M to 1,2,3,4-tetrazine-1,3-dioxides. Two combination rules were invented, they were simple single-points rule and double-points rule. All the structures are ring-fused or caged compounds including 1,2,3,4-tetrazine-1,3-dioxide. In these compounds, almost half of them have positive or zero oxygen balances, and the nitrogen contents of 17 compounds are over 40%. The densities and detonation velocities of all compounds are over 1.98 g cm-3 and 9500 m s-1 respectively. -N = N- group and -NO2 group have a major contribution to enthalpy of formation, detonation heat, and power index. -O- group and -ONO2 group have the main contribution to density, detonation velocity, and detonation pressure.

Theoretical study of the effect of N-oxides on the performances of energetic compounds.

In order to study the effects of N-oxide on structure and performance, six categories of energetic compounds were systemically investigated. The results indicated that the C-C bonds in the rings were shortened, and the C-N bonds close to the N → O bond were elongated when N atoms was oxidized to form N → O bonds. N → O bonds can increase the densities of most categories of compounds, and the increment will increase with the number of N → O bonds. As to their detonation performances, almost all categories of compounds had an increased trend, except for some NO2-, NHNO2- and ONO2-substituted compounds. The contribution of 1,2,3,4-tetrazine and 1,2,4,5-tetrazine to performances was better than that of pyrazine and [1,2,5] oxadiazolo [3,4-b] pyrazine on the whole, and the groups, especially energetic groups, made a huge contribution to performance. When R was a NH2 or ONO2 group, all compounds had lower impact sensitivities, and thus represent candidates for novel energetic compounds. However, other than the sixth category of compounds, all compounds had higher impact sensitivities when R was a NO2 or NHNO2 group, and have little significance in application.

Reaction Mechanism of 3,4-Dinitrofuroxan Formation from Glyoxime: Dehydrogenation and Cyclization of Oxime.

The reaction pathway of the formation of 3,4-dinitrofuroxan from glyoxime is theoretically investigated under experimental conditions with 25 % nitric acid and dinitrogentetroxide reagents to clarify the mechanism of formation of a furoxan ring by glyoxime. The geometric configurations of minima and transition-state species are optimized at the (U)B3LYP/6-311++G** level. The CCSD(T) and CASSCF(10e,8o)/CASSCF(9e,8o) single-point energy corrections at the same level are performed on top of the optimized geometries. A subsequent dynamic correlation by using NEVPT2/6-311++G**-level single-point energy calculations based on the CASSCF results is also performed to obtain accurate energy values. The formation reaction is analyzed from two processes: glyoxime nitration and 3,4-dinitroglyoxime (nitration product) oxidative cyclization. Calculation results indicate that the electrophilic substitution of nitronium ions from the protonated HNO3 and the abstraction of hydrogen ions by HNO3 molecules are requisites of glyoxime nitration. The formation of a furoxan ring from 3,4-dinitroglyoxime involves two possible mechanisms: 1) oxydehydrogenation by NO2 molecules and the subsequent torsion of NO radical groups to form a ring and 2) the alternation of dehydrogenation and cyclization. The intermediates and transition states in both routes exhibit monoradical and diradical characteristics. Singlet and triplet reactions are considered for the diradical species. Results show that the singlet reaction mechanism is more favorable for cyclization than the triplet reaction. The formation of a furoxan ring from oxime is in accordance with the stepwise intermolecular dehydrogenation and intramolecular torsion to the ring.

Design and theoretical study of 15 novel high energy density compounds.

In order to seek the potential high energy density compounds (HEDCs) with excellent performance and satisfactory safety, some combination rules are presented and 15 HEDCs are designed and sifted, and followed by the properties predicting. From the results, HEDC-3, HEDC-4, HEDC-9, HEDC-10, HEDC-11, HEDC-12, HEDC-13, and HEDC-14 have good comprehensive properties. They are furoxan, fused ring or cage-type compounds, whose frame is composed of some single ring by single (double or multi) point addition. Their densities are over 1.95 g cm(-3), and detonation velocities are over 9500 m s(-1). Their BDEs are over 85 kJ mol(-1), and the values of available free space (∆V) are lower than the ∆V of ß-CL20 (∆V = 86). In view of the synthesis feasibility, the synthesis routes of HEDC-4, HEDC-9, HEDC-10, HEDC-12, HEDC-13, and HEDC-14 have been designed.

Theoretical study on the structure and stability of [1,2,5] oxadiazolo [3,4-e] [1,2,3,4]-tetrazine-4,6-Di-N-dioxide (FTDO).

Although many 1,2,3,4-tetrazine-1,3-dioxide derivates have been synthesized, [1,2,5] oxadiazolo [3,4-e] [1,2,3,4]-tetrazine-4,6-di-N-dioxide (FTDO) is the only one with high enthalpy of formation and high detonation velocity. Whereas, its stability has not been studied. In the present work, the structure of FTDO was investigated using density functional theory (DFT) method, and its stability was calculated by potential energy surface scanning and structure interconvert thermodynamics under different temperatures. The spontaneous isomerization of FTDO and its effect on the stability of FTDO were investigated. The dissociation of FTDO to N2, N2O and furoxan fragments was studied, and the possibility of synthetic route from FTDO to TTTO was discussed.

The effect of microdroplet size on the surface tension and Tolman length.

A monomolecular layer model of the surface phase of microdroplets was proposed, and the exact expression for Tolman length was derived in this paper. The Tolman lengths of water, n-pentane, and n-heptane were calculated by the expression, and the values are quite in agreement with the experimental values. By use of the Gibbs-Tolman-Kening-Buff equation, the exact relationship between the microdroplet surface tension and the radius is obtained, and the predicted values agree well with the simulated values. The results show that there is an obvious effect of the size of microdroplets (or nanoparticles) on the surface tension, and the surface tension decreases with decreasing droplet size. For the microdroplets of general liquid, only if their radius approaches or reaches 10(-9) m does the effect become significant.

Nitrosation of malononitrile by HONO, ClNO and N2O3: a theoretical study.

Nitrosation reactions of malononitrile by three nitrosating agents, HONO, ClNO, and N(2)O(3), have been theoretically investigated at the B3LYP/cc-pVTZ and MP2/cc-pVDZ levels. Two possible competitive paths for nitrosation of malononitrile to give 2-nitroso-malononitrile were proposed: (a) direct C-nitrosation and (b) N-nitrosation and subsequent nitroso transfer from N to C atom. The calculations show that at both B3LYP and MP2 levels, path b is kinetically favored over path a for nitrosations by HONO and N(2)O(3). In the case of ClNO, the B3LYP predicts preference of path b, while the MP2 calculations suggest that both paths have similar rate-determining barriers. The data suggest that N(2)O(3) is the preferred nitrosating agent for the nitrosation of malononitrile in aqueous solution. Transformation of 2-nitroso-malononitrile to form malononitrileoxime via intramolecular proton transfer has also been explored, and it is found that inclusion of an assistant water molecule can drastically accelerate the tautomerization.