Nitroamino Group Research Articles

Host-Guest Technique for Designing Highly Energetic Compounds with the Nitroamino Group.

A new energetic material, 2-azido-4,7-nitroamino-1H-imidazo[4,5-d]pyridazine (ANIP) with a highly sensitive azido group and its host-guest compounds (ANIP/H2O and ANIP/H2O2), and energetic salts were obtained. With the guest and protons in host molecules, an abundant hydrogen bond system can be formed. This results in high crystal density and good sensitivity, which suggests that the host-guest strategy is a promising way to balance the contradiction between energy and sensitivity and provides a new path to obtain a new generation of high energetic materials.

Obtaining superior high-density fused-ring energetic materials via the introduction of carbonyl, o-NH2-NO2 and nitroamino groups.

Two carbonyl and o-NH2-NO2-containing energetic materials and their analogues were effectively designed, synthesized and fully characterized with multinuclear NMR, IR and elemental analyses. Their structures were also further confirmed via X-ray diffraction. Among them, compound 7 exhibits good potential for application as a secondary explosive with extremely high density (2.04 g cm-3), good sensitivity (IS > 40 J, FS > 360 N), and excellent calculated detonation performance (Dv = 8943 m s-1, P = 35.0 GPa). Furthermore, a detailed comparative study based on X-ray diffraction, Hirshfeld surfaces and 2D fingerprint plots among compounds 4, 7 and 9 has demonstrated that the density and detonation performance could be effectively improved via introducing a carbonyl group into fused-ring compounds. More importantly, the sensitivity of the resulting energetic materials did not deteriorate. Obviously, this strategy via introducing carbonyl, o-NH2-NO2 and nitroamino groups into fused-ring energetic compounds will help in the design of next-generation high-energy and insensitive fused-ring energetic materials.

Assembling Nitroamino and Amino Groups on a Pyrazolyl-1,3,4-Oxadiazole Framework for the Construction of High-Performance and Insensitive Energetic Materials

AbstractThe introduction of nitroamino groups onto a nitrogen-rich heterocyclic skeleton is an efficient method for constructing high-performance energetic compounds. In this work, the nitroamino-functionalized compound 4-(5-amino-1,3,4-oxadiazol-2-yl)-N,N′-dinitro-1H-pyrazole-3,5-diamine was synthesized in yields of up to 83%. In addition, its energetic salts were also prepared. All these compounds were characterized by NMR and IR spectroscopy and, in two cases, by single-crystal X-ray diffraction. In addition, the difference in the reactivities of the three amino groups on the pyrazolyloxadiazole system was analyzed by an average local ionization energy analysis. The hydrazinium salt of the diamine exhibits promising detonation properties and good molecular stability, suggesting it has good application potential. Compared with previous works, this strategy gives an improved isolated yield and provides a promising method for the construction of nitroamino-functionalized 1,3,4-oxadiazole derivatives.

Highly Selective Nitroamino Isomerization Guided by Proton Transport Dynamics: Full-Nitroamino Imidazole[4,5-d]pyridazine Fused-Ring System.

Due to the advantage of the hydrogen bond system formed by nitroamino isomerization, by the calculations of hydrogen transfer in reported nitroamino explosives, the proton transport dynamics was first proposed to predict the nitroamino isomerization of energetic materials. With the calculated results of zero-point energy, the full-nitroamino fused energetic materials, 2,4-nitroamino-7-nitroimino-1,5-dihydro-4H-imidazolo[4,5-d]pyridazine (FNPI-1) and 2,2',7,7'-tetranitromino-4,4'-azo-imidazolo[4,5-d]pyridazine (FNPI-2) were designed and successfully synthesized. The highly selective nitroamino isomerization of neutral compound FNPI-1 is shown by X-ray diffraction. After the hydrogen transfer occurs, the intermolecular hydrogen bonds will greatly promote tight stacking, which enhances the density and thus a series of comprehensive properties of energetic materials. The theoretical calculations of zero-point energy explain perfectly the selectivity of hydrogen transfer between the nitroamino groups and the fused-ring skeleton for FNPI-1. The hydrogen atom transfer and selective isomerization of nitroamino energetic materials can be accurately predicted following proton transport dynamics, which provides computational bases and new ideas for the efficient design of fully nitroamino-based explosives.

Single-Crystal Diffraction, Raman Spectroscopy, and Density Functional Theory of DTO [N-(1,7-Dinitro-1,2,6,7-tetrahydro-[1,3,5]triazino[1,2-c][1,3,5]oxadiazin-8(4H)-ylidene)nitramide

A combined experimental and modeling study of energetic compound N-(1,7-dinitro-1,2,6,7-tetrahydro-[1,3,5]triazino[1,2-c][1,3,5]oxadiazin-8(4H)-ylidene)nitramide [C5H6N8O7, (DTO)] has been performed. We report its crystal structure, solid-phase heat of formation, and its vibrational and electronic structure obtained by single-crystal X-ray diffractometry, Raman spectroscopy, and density functional theory (DFT). DTO exhibits two adjoining six-membered rings, a triazine ring (C3N3) and an oxadiazine ring (C3N2O) ring containing two nitro functional groups and one nitroamino group. DTO crystallizes with four molecules in its unit cell and presents a density of 1.862 kg/m3 at 298 K, in excellent agreement with both DFT calculations performed both at the molecular level using the B3LYP with the 6-311+G** basis set and the solid-state level using the hybrid functional HSE6 optimized with norm-conserving pseudopotentials. The calculated vibrational structure allows for the symmetry assignment of key Raman modes in terms of atomic movements, and the calculated frequency values are in good agreement with experiment. The solid-phase DFT calculations reveal that the N atoms of the triazine ring contribute mostly to the density of states at the Fermi level. In addition, we present and discuss the computed solid-phase heat of formation (215.9 kJ/mol) and molecular electrostatic potential surface of DTO and compare them to complementary materials.

Energetic compounds based on a new fused triazolo[4,5-d]pyridazine ring: Nitroimino lights up energetic performance

The difference between nitroimino and nitroamino in compound 5. • A new triazolo[4,5–d]pyridazine fused ring was synthesized. • A different method was found to synthesize the pyridazine fused ring. • The nitroimino group has a low ESP and forms strong HB and π-π interactions. • The properties of compounds 7 and 8 are comparable to those of HMX. • The synthesis of 5 is cost effective and can be extended to gram-scale (2 g). A series of highly energetic materials with good detonation performance, high density and low impact sensitivity based on a new triazolo[4,5–d]pyridazine fused ring was synthesized and characterized. 4-Nitroamino-7-nitroimino-triazolo[4,5–d]pyridazine ( 5 ) was characterized by single crystal X-ray structure analysis, which shows that the proton of one nitroamino group was transferred to the pyridazine ring forming a nitroimino moiety. The electrostatic potential (ESP) of 5 shows the nitroimino group has the lowest negative value, while the nitroamino area has a high positive value. The analysis of NCI plots indicates strong intramolecular hydrogen bonds (HB) and π-π interactions which arise from the newly formed nitroimino group. This supports that the rearrangement of the nitroamino group to form the nitroimino moiety lowers the impact sensitivity. Compound 5 ·H 2 O exhibits face-to-face packing, which gives rise to a relatively high density of 1.87 g cm −3 and a low impact sensitivity of 18 J. Its hydrazinium and hydroxylammonium salts have high detonation velocities of 9351 m s −1 and 9307 m s −1 , respectively. Their impact and friction sensitivities (7 J, 120 N and 8 J, 160 N) are similar to HMX. This proclivity for rearrangement by a nitroamino group provides new insight into the design of next generation high energy density materials.

Embellishing bis-1,2,4-triazole with four nitroamino groups: advanced high-energy-density materials with remarkable performance and good stability

Tetranitroamino HEDMs based on bis-triazole with comparable performance to CL-20 (D: 9421 and 9609 m s−1) and superior stability.

Asymmetric nitrogen-rich energetic materials resulting from the combination of tetrazolyl, dinitromethyl and (1,2,4-oxadiazol-5-yl)nitroamino groups with furoxan.

Three classes of nitrogen-rich energetic compounds 7-9 (combination of tetrazolyl, dinitromethyl and furoxan), 12-17 (combination of tetrazolyl, (1,2,4-oxadiazol-5-yl)nitroamino and furoxan) and 20-22 (combination of dinitromethyl, (1,2,4-oxadiazol-5-yl)nitroamino and furoxan) were obtained by selected reactions with 3,4-dicyano-furoxan. All the new compounds were thoroughly characterized by IR, NMR [1H, 13C{1H}], elemental analysis, and differential scanning calorimetry (DSC). Compounds 7, 13, 20 and 22 were also further characterized with single-crystal X-ray diffraction studies. Heats of formation and detonation performances for nine compounds were determined using Gaussian 03 and EXPLO5 v6.01 programs, showing that 15 as a secondary explosive is superior to 1,3,5-trinitrotriazacyclohexane (RDX) and 20 is a promising green primary explosive.

Preparation, morphologies and thermal behavior of high nitrogen compound 2-amino-4,6-diazido-s-triazine and its derivatives

The crystal morphologies, thermal behavior, sensitivity and performance of 2-amino-4,6,-diazido-s-triazine and its derivatives have been investigated using SEM, DSC, TG techniques and related theories. It has been shown that the DANT crystal is in 1–5μm thickness layered regular hexagon structure with severe agglomeration. DAAT crystal is very hydrophobic and can be dispersed in water, which has layered rectangle structure with thickness less than 0.5μm. The TAHT materials exist in a form of amorphous irregular particles with diameters of more than 200μm while its analogue TAAT can be crystallized in needle shape with a length of 30μm. TNADAzT crystal has a shape of regular polyhedron with average size of about 120μm. The thermal analysis indicates that there is only one complex step for decomposition of DAAT, while at least three steps are included for the other materials. DAAT started to decompose at around 148.4°C with a peak temperature of 197.0°C, while TAHT started to decompose at 167.2°C with shoulder-peak of 193.4–206.7°C at the heating rate of 2.0°Cmin−1. DANT decomposes with a heat release of 2420–2721Jg−1, which is much higher than that of DAAT indicating that the heat and its release rate are greatly enhanced by transformation of amino to nitroamino group. Different from the analogue TAHT, there is an obvious melting process at about 152°C before TAAT decomposition covered by an enthalpy of fusion 93–100Jg−1. The thermal stability of TNADAzT is slightly worse than that of DAAT, and it decomposes in liquid state with a melting point of about 171°C.

Thermal Decomposition Mechanism of 2-Nitroimino-5-Nitro-Hexahydro-1,3,5-Triazine (NNHT)

The thermal properties and the decomposition mechanism of 2-nitroimino-5-nitro-hexahydro-1,3,5-triazine (NNHT) were studied by DSC-TG-IR-MS technology. The results show that the hexahydric ring framework cracking and the nitroamino group [NNO2] breaking induce to the major exothermic decomposition process. The gaseous products are H2O, N2, CO2, N2O, HCHO, NH3, CH2, NH2, CHO, HCN, HNCO, and NO2.

Substituent effect on the molecular stability, group interaction, detonation performance, and thermolysis mechanism of nitroamino-substituted cyclopentanes and cyclohexanes

Density functional theory (DFT) method has been employed to study the effect of nitroamino group as a substituent in cyclopentane and cyclohexane, which usually construct the polycyclic or caged nitramines. Molecular structures were investigated at the B3LYP/6-31G** level, and isodesmic reactions were designed for calculating the group interactions. The results show that the group interactions accord with the group additivity, increasing with the increasing number of nitroamino groups. The distance between substituents influences the interactions. Detonation performances were evaluated by the Kamlet-Jacobs equations based on the predicted densities and heats of formation, while thermal stability and pyrolysis mechanism were studied by the computations of bond dissociation energy (BDE). It is found that the contributions of nitroamino groups to the detonation heat, detonation velocity, detonation pressure, and stability all deviate from the group additivity. Only 3a, 3b, and 9a–9c may be novel potential candidates of high energy density materials (HEDMs) according to the quantitative criteria of HEDM (ρ ≈ 1.9 g/cm3, D ≈ 9.0 km/s, P ≈ 40.0 GPa). Stability decreases with the increasing number of N-NO2 groups, and homolysis of N-NO2 bond is the initial step in the thermolysis of the title compounds. Coupled with the demand of thermal stability (BDE > 20 kcal/mol), only 1,2,4-trinitrotriazacyclohexane and 1,2,4,5-tetranitrotetraazacyclohexane are suggested as feasible energetic materials. These results may provide basic information for the molecular design of HEDMs.

Substituent Effect on Infrared Spectra and Thermodynamic Properties of Polynitroamino Substituted Cyclopentane and Cyclohexane

Density functional theory method was employed to study the effect of the nitroamino group as a substituent in cyclopentane and cyclohexane, which usually construct polycyclic or caged nitramines. Based on the optimized molecular structures of two groups of monocyclic nitramines at the B3LYP/6-31G** level, the infrared (IR) spectra were obtained and assigned by harmonic vibrational analysis. The calculated results agree reasonably with the available experimental data. According to the principles of statistic thermodynamics, thermodynamic properties were derived from the IR spectra, which were linearly correlated with the number of nitroamino groups as well as the temperature. The contributions of nitroamino groups to thermodynamic properties are in accord with the group additivity.

Theoretical Studies on Thermolysis Mechanism and Stability of trans‐1,4,5,8‐Tetranitro‐1,4,5,8‐tetraazadecalin Isomers

AbstractA systematic study on the thermolysis mechanism and stability of a series of energetic cyclic nitramines, trans‐1,4,5,8‐tetranitro‐1,4,5,8‐tetraazadecalin isomers, was performed by density functional theory (DFT) and semiempirical molecular orbital (MO) calculations. Bond dissociation energies (BDE) and activation energies (Ea) of the thermolysis processes were computed at the B3LYP/6‐31G∗︁∗︁ and PM3 levels, respectively. The effect of nitroamino groups on the thermal stability and pyrolysis mechanism of the title compounds was evaluated by the BDE and Ea. The correlations among BDE, Ea, bond overlap populations, energies of the frontier orbitals, and energy gaps were examined in detail. The results indicate that thermal stabilities and decomposition mechanisms of the title compounds derived from the BDE, Ea and static electronic parameters are basically consistent. Homolysis of the N–NO2 bond is the initial step in the thermolysis of the title compounds, the meta‐isomers are more stable than the para‐isomers, and the ortho‐isomers are the most sensitive.

2-Nitroguanidine Derivatives: V. Synthesis and Structure of 3,5-Bis(nitroamino)-1,2,4-triazole Salts. Acid–Base Properties of 3,5-Bis(nitroamino)-1,2,4-triazole

Heterocyclization of hydrazine-1,2-bis(N 2-nitrocarboximidamide) and salts derived therefrom provides a procedure for the synthesis of 3,5-bis(nitroamino)-1,2,4-triazole salts. The presence of two acceptor nitroamino groups conjugated with the triazole ring considerably enhances the acidity of 3,5-bis(nitroamino)-1,2,4-triazole (pK a1= –2.0, pKa2 = 4.8, pKa3 = 10.6) as compared to mononitroaminotriazole, so that formation of salts with the corresponding dianion becomes possible.

4-Chloro-N-methyl-N-nitroaniline

The molecular structure of (p-ClC6H4)(CH3)NNO2 (or C7H7ClN2O2) contains a planar NNO2 nitroamino group which is twisted about the N—Cphenyl bond by ca 68° from the plane of the aromatic ring. The structural data are in agreement with the spectral results and indicate that there is no conjugation between the aromatic sextet and the nitroamino group. There are no specific intermolecular interactions.

Conformation and circular dichroism of some N-nitropyrrolidines

The results of a theoretical investigation (ab initio calculations) of the parent nitropyrrolidine 1 and its (R)-2-methyl and (R,R)-2,5-dimethyl derivatives 2, 3 are in good agreement with the CD, UV and 1H NMR spectra of 2, 3 and the X-ray analysis of 3. In the ground state of nitropyrrolidines l, 2 both nitrogen atoms of the nitroamino group are pyramidal and both nitrogen atoms of 3 are planar. In all cases, a small twisting of the nitroamino group about the N–N bond is observed. An envelope conformation with the C4 atom at the tip is predicted for nitropyrrolidine 1 and the more stable isomer 2a, which has a pseudoaxial methyl group. The less stable isomer 2b, (with a pseudoequatorial methyl group) and both isomers of 3 (2,5-di-pseudoaxial 3a and 2,5-di-pseudoequatorial 3b) adopt a half-chair conformation. In solutions and the crystal state, 3 exists as isomer 3a. Four Cotton effects are observed in the CD spectra of 2, 3. The signs of the Cotton effect at 270, 240 and 200 nm (the no+–π*, πN–π* and πo–π* electronic transitions) are determined by the configuration of the α-carbon chiral centres. The intrinsic chirality of the nitroamino chromophore and the chirality of the five-membered ring influence, mostly, the Cotton effect of the no––π* transition at 300 nm.

Polarizability anisotropy of the nitroamino group and the conformations of some substituted nitroamines

1. The major semiaxes of the polarizability ellipse for the C2NNO2 group were determined (5.36, 4.25, 2.10 A3). 2. The conformations of the nitroamines correspond approximately to the eclipsing of one of the bonds of theα carbon atom and the NO2 group. 3. In the N-nitroso-N-alkylbenzenesulfonamides the alkyl radical eclipses the S=O bond.