Synthesis of Energetic 7-Nitro-3,5-dihydro-4H-pyrazolo[4,3-d][1,2,3]triazin-4-one Based on a Novel Hofmann-Type Rearrangement.

Rearrangement reactions are efficient strategies in organic synthesis and contribute enormously to the development of energetic materials. Here, we report on the preparation of a fused energetic structure of 7-nitro-3,5-dihydro-4H-pyrazolo[4,3-d][1,2,3]triazin-4-one (NPTO) based on a novel Hofmann-type rearrangement. The 1,2,3-triazine unit was introduced into the fused bicyclic skeleton from a pyrazole unit for the first time. The new compound of NPTO was fully characterized using multinuclear NMR and IR spectroscopy, elemental analysis as well as X-ray diffraction studies. The thermal behaviors and detonation properties of NPTO were investigated through a differential scanning calorimetry (DSC-TG) approach and EXPLO5 program-based calculations, respectively. The calculation results showed similar detonation performances between NPTO and the energetic materials of DNPP and ANPP, indicating that NPTO has a good application perspective in insensitive explosives and propellants.

Mechanisms and risk assessments on the N-nitration of N-acetylhexahydro-s-triazines: understanding the preparation of RDX (2).

Although the N-nitration by nitric acid is widely used to synthesize nitramines in biological, medical, and explosive industries, little is known about the microscopic behavior when the nitrated substrates are tertiary amines. Hexahydro-1,3,5-triacetyl-s-triazine (TRAT) nitrated into hexahydro-1,3,5-trinitro-s-triazine (RDX) was theoretically investigated at the MP2/cc-PVDZ level. An O-to-N transnitration mechanism was put forward for the N-nitration of N-acetyl tertiary amines, including the formation of diverse complexes R'N(COCH3)RNO2(+) and deacetylate. The electron transfer results in the complex formation, and the acetyl-to-nitro electrophilic displacement leads to deacetylate. Presumably, the carbonyl groups (C═O) in N-acetyl tertiary amines serve as the hinged joint in the electron transfer. Three successive N-nitrations transform TRAT into RDX; their electron transfers are strongly exothermic by -21.1, -19.5, and -15.4 kcal/mol relative to TRAT + 3NO2(+), repectively, and their electrophilic displacements possess low activation Gibbs free energies of 9.0, 6.8, and 7.5 kcal/mol relative to the σ-complexes 6, 11, and 14, respectively. The rate constants of the single electron transfer (SET) and the acetyl-to-nitro displacement were estimated roughly by Marcus and transition-state (TS) theories, respectively, indicating that they are both fast with the strong exothermicity. The available experimental phenomena were well interpreted by the computational results.

Carbamo-yl(di-amino-methyl-idene)aza-nium 3-nitro-5-oxo-4,5-di-hydro-1H-1,2,4-triazol-4-ide.

In the anion of the title salt, C2H7N4O(+)·C2HN4O3 (-), the negative charge resides formally on the N(3) atom of the triazole ring. In the crystal, the N(3) and exocyclic O atoms are hydrogen-bond acceptors with respect to the formally double-bond iminium and amido N atoms of the cation. The cation and anion are almost planar (r.m.s. deviations = 0.012 and 0.051 Å, respectively), but they are slightly bent with respect to each other [dihedral angle = 12.6 (1)°]. In the crystal, adjacent anions and cations are linked by extensive N-H⋯N and N-H⋯O hydrogen bonds, generating a ribbon running along the b-axis direction.

An environment friendly electrochemical synthesis of 1,1,4,4-tetramethyl-2-tetrazene energetic materials from undimethylhydrazine.

As a prospective alternative liquid propellant, 1,4,4-tetramethyl-2-tetrazene (TMTZ) possesses high enthalpy of formation and environment friendly decomposition products, and shows a promising application prospect in aerospace, munitions manufacturing, etc. An environment friendly and convenient synthesis of TMTZ through electrochemical oxidative coupling of undimethylhydrazine (UDMH) on commercially procured electrodes was carried out under mild conditions, in which the purity is up to 98.5% with a yield of over 45%. It is a simple, clean and suitable method for industrial production in contrast with the previously reported conventional chemical oxidation syntheses.

4,9,12,15-Tetra-oxa-3,5,8,10,14,16-hexa-aza-tetra-cyclo-[11.3.0.0.0]hexa-deca-1(16),2,5,7,10,13-hexaen-3-ium-3-olate monohydrate.

The organic mol-ecule in the title monohydrate, C(6)N(6)O(5)·H(2)O, presents an almost planar configuration, the greatest deviation from the least-squares plane through the atoms being 0.061 (1) Šfor the O atom within the seven-membered ring. Each water H atom is bifurcated, one forming two O-H⋯N hydrogen bonds and the other forming O-H⋯N,O hydrogen bonds. The result of the hydrogen bonding is the formation of supra-molecular layers with a zigzag topology that stack along [001].

Diethyl 2,2'-bis-(hy-droxy-imino)-3,3'-(hydrazinediyl-idene)dibutano-ate.

Each mol-ecule of the title compound, C(12)H(18)N(4)O(6), is located on an inversion centre at the mid-point of the central N-N bond. The azo groups C=N of the Schiff base group have an E conformation and the azo groups in the oxime C=N-O groups have a Z conformation. O-H⋯O hydrogen bonds link neighbouring mol-ecules into infinite monolayers perpendicular to the a axis.

4-[4-(4-Amino-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazol-3-yl]-1,2,5-oxadiazol-3-amine.

The complete molecule of the compound, C(6)H(4)N(8)O(3), is generated by a crystallographic twofold rotation axis that runs through the central ring. The flanking ring is twisted by 20.2 (1)° with respect to the central ring. One of the amino H atoms forms an intra-molecular N-H⋯N hydrogen bond; adjacent mol-ecules are linked by N-H⋯N hydrogen bonds forming a chain running along [10-2].

2-tert-Butyl-1-(4-nitro-amino-1,2,5-oxadiazol-3-yl)diazene 1-oxide.

In the title compound, C(6)H(10)N(6)O(4), the nitro-amine -NHNO(2) substituent and the C-N=N(→ O) unit of the other substituent of the oxadiazole ring are nearly coplanar with the five-membered ring [dihedral angles = 5.7 (1) and 3.0 (1)°]. The amino group of the -NHNO(2) substituent is a hydrogen-bond donor to the two-coordinate N atom of the C-N=N(→ O) unit.

A Family of Energetic Materials Based on 1,2,4-Oxadiazole and 1,2,5-Oxadiazole Backbones With Low Insensitivity and Good Detonation Performance.

Design and synthesis of new compounds with both high detonation performances and good safety properties have always been a formidable task in the field of energetic materials. By introducing -ONO2 and -NHNO2 moieties into 1,2,4-oxadiazole- and 1,2,5-oxadiazole-based backbones, a new family of energetic materials, including ammonium 3-nitramino-4-(5-hydroxymethyl-1,2,4-oxadiazol-3-yl)-furazan (4), 3,3'-bis[5-nitroxymethyl-1,2,4-oxadiazol-3-yl]-4,4'-azofuroxan (6), [3-(4-nitroamino-1,2,5-oxadiazol-3-yl)-1,2,4-oxadiazol-5-yl]-methylene nitrate (8), and its energetic ionic salts (10-12), were synthesized and fully characterized. The energetic and physical properties of the materials were investigated through theoretical calculations and experimental determination. The results show that the oxadiazole-based compounds exhibit high enthalpy of formations, good detonation performances, and extraordinary insensitivities. In particular, the hydrazinium salt (11) shows the best energetic properties (11: d = 1.821 g cm-3; P = 35.1 GPa, v D = 8,822 m s-1, IS = 40 J, FS > 360N). The ESP and Hirshfeld surface analysis indicated that a large number of hydrogen bonds as well as π-π stacking interactions within molecules might be the key reason for their low sensitivities and high energy-density levels.

An Ag(I) energetic metal-organic framework assembled with the energetic combination of furazan and tetrazole: synthesis, structure and energetic performance.

A novel Ag(I) energetic MOF [Ag16(BTFOF)9]n·[2(NH4)]n () assembled with Ag(iI ions and a furazan derivative, 4,4'-oxybis[3,3'-(1H-5-tetrazol)]furazan (H2BTFOF) was successfully synthesized and structurally characterized, featuring a three-dimensional porous structure incorporating ammonium cations. The thermal stability and energetic properties were determined, revealing that the 3D energetic MOF had an outstanding insensitivity (IS > 40 J), an ultrahigh detonation pressure (P) of 65.29 GPa and a detonation velocity (D) of 11.81 km cm(-3). In addition, the self-accelerating decomposition temperature (TSADT) and the critical temperature of thermal explosion (Tb) are also discussed in detail. The finding exemplifies that the assembly strategy plays a decisive role in the density and energetic properties of MOF-based energetic materials.

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.

Thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety and burning rates of BTATz-CMDB propellant.

The composite modified double base (CMDB) propellants (nos. RB0601 and RB0602) containing 3,6-bis (1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz) without and with the ballistic modifier were prepared and their thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety and burning rates were investigated. The results show that there are three mass-loss stages in TG curve and two exothermic peaks in DSC curve for the BTATz-CMDB propellant. The first two mass-loss stages occur in succession and the temperature ranges are near apart, and the decomposition peaks of the two stages overlap each other, inducing only one visible exothermic peak appear in DSC curve during 350-550 K. The reaction mechanisms of the main exothermal decomposition processes of RB0601 and RB0602 are all classified as chemical reaction, the mechanism functions are f(alpha)=(1-alpha)(2), and the kinetic equations are dalpha/dt = 10(19.24)(1-alpha)(2)e(-2.32x10(4)/T) and dalpha/dt = 10(20.32)(1-alpha)(2)e(-2.32x10(4)/T). The thermal safety evaluation on the BTATz-CMDB propellants was obtained. With the substitution of 26% RDX by BTATz and with the help of the ballistic modifier in the CMDB propellant formulation, the burning rate can be improved by 89.0% at 8 MPa and 47.1% at 22 MPa, the pressure exponent can be reduced to 0.353 at 14-20 MPa.

Non-isothermal thermal decomposition reaction kinetics of 2-nitroimino-5-nitro-hexahydro-1,3,5-triazine (NNHT).

The thermal behavior and decomposition reaction kinetics of 2-nitroimino-5-nitro-hexahydro-1,3,5-triazine (NNHT) were investigated by TG-DTG and DSC under atmospheric pressure and flowing nitrogen gas conditions. The results show that the thermal decomposition process of NNHT has two mass loss stages. The exothermic decomposition reaction mechanism obeys chemical reaction rule. The kinetic parameters of the reaction are E(a)=131.77 kJ mol(-1), lg(A/s(-1))=12.56, respectively. The kinetic equation can be expressed as: dalpha/dt = 10(12.86)(1-alpha)(3/2)3(-1.5849 x 10(4)/T)). The critical temperature of thermal explosion of NNHT obtained from the peak temperature (T(p)) is T(bp)=467.22K. The entropy of activation (DeltaS( not equal)), enthalpy of activation (DeltaH( not equal)), and free energy of activation (DeltaG( not equal)) of the reaction are -7.978 J mol(-1)K(-1), 127.99 kJ mol(-1) and 131.62 kJ mol(-1), respectively.