Nitramino Group Research Articles

Energetic N‐Nitramino‐Substituted 1,2,4‐Triazole and Corresponding Salts: Green Primary Explosives with Excellent Detonation Performance Based on 1,5‐Diamino‐3‐nitro‐1,2,4‐triazole

Abstract5‐amino‐3‐nitro‐1‐nitramino‐1,2,4‐triazole was synthesized through the nitration reaction of 1,5‐diamino‐3‐nitro‐1,2,4‐triazole, and several energetic salts were prepared based on the reactivity of the acidic proton in nitramino group (−NHNO2). These compounds were fully characterized by NMR (1H and 13C), IR spectroscopy, elemental analysis, and single‐crystal X‐ray diffraction. Their thermal stabilities were analyzed by differential scanning calorimetric (DSC) and Impact and friction sensitivities were determined using standard BAM technology. Moreover, the structural differences between individual compounds were studied to investigate the potential structure‐property relationship. All compounds possess positive heats of formation calculated based on isodesmic reaction to be between 173.7~454.6 kJ ⋅ mol−1. Among them, 5‐amino‐3‐nitro‐1‐nitramino‐1,2,4‐triazole (D=8682 m ⋅ s−1, P=33.0 GPa, IS=0.75 J), hydrazine salt (D=8908 m ⋅ s−1, P=34.9 GPa, IS=0.5 J) and hydroxylamine salt (D=9117 m ⋅ s−1, P=36.7 GPa, IS=2 J) exhibits desirable detonation properties similar to RDX (D=8795 m ⋅ s−1, P=34.9 GPa), calculated by Kamlet‐Jacobs equations and features comparable impact sensitivity with DDNP (IS=1 J). The simple synthetic route, free of heavy metals and superior detonation properties of above compounds make them serve as promising candidate for green primary explosives.

Energetic Coordination Polymers Based on Copper Furazans and 1,2,3-Triazoles: Tuning the Oxygen Balance with Nitramino Functionalities

Four novel energetic complexes comprising furazan/nitramino groups were synthesized through a simple hydrothermal method. Owing to the introduction of an oxygen-containing nitramino group, Cu(DNAF)(NH3)3 (ECP-1), Cu(DNAF)(H2O)3 (ECP-2), Cu(ANFZ)2(H2O)5 (ECP-3), and Cu2(TA)2(H2O)6 (ECP-4) (DNAF = 4,5-dinitraminofurazan, ANFZ = 4-amino-3-nitraminofurazan, TA = 5-nitro-4-nitramino-1,2,3-triazole) possess relatively high oxygen contents and oxygen balance, indicating efficient energy release during the self-sustained redox process. In addition, these energetic coordination polymers (ECPs) possess exceptional crystal density and insensitivity to external stimuli. Compared to the energetic complexes reported previously, the oxygen balance and contents of nitrogen and oxygen atoms of ECP-1–ECP-4 remain at a relatively higher level (OB > −20%, N+O% > 60%), ECP-2 and ECP-4 have excellent positive oxygen balance (10.5% and 5.5%, respectively), and ECP-4 has the highest density (2.22 g/cm3) among these four coordination polymers.

THEORETICAL CALCULATIONS ABOUT THE THERMAL STABILITY AND DETONATION CHARACTER OF NITRAMINO-SUBSTITUTED PYRROLE

A series of nitramino-derivatives of pyrrole were designed through introducing the nitramino group into pyrrole ring to look for high-energy-density compounds. The molecular stabilities are explored thoroughly based on the calculated heats of formation, bond dissociation energy, and bond order at the B3PW91/6-311+G(d,p) level. The results indicated that the molecules designed in this paper have enough stability not only thermally but also kinetically. To evaluate the potential application as high-energy-density compounds, the detonation velocity and detonation pressure are calculated by using the Kamlet-Jacobs equation. Based on the calculation both of stability and detonation characters, four nitramino-derivatives of pyrrole (D1: 2,3-trinitramino-1H-pyrrole, D2: 2,3,4-trinitramino-1H-pyrrole, D3: 2,3,5-trinitramino-1H- pyrrole and E: 2,3,4,5- tetranitramino- 1H-pyrrole) are screened out as potential high-energy-density molecules for further study.

Theoretical studies on a new furazan compound bis[4-nitramino-furazanyl-3-azoxy]azofurazan (ADNAAF).

Bis[4-nitraminofurazanyl-3-azoxy]azofurazan (ADNAAF), synthesized in our previous work [1], contains four furazan units connected to the linkage of the azo-group and azoxy-group. For further research, some theoretical characters were studied by the density functional theoretical (DFT) method. The optimized structures and the energy gaps between the HOMO and LUMO were studied at the B3LYP/6-311++G** level. The isodesmic reaction method was used for estimating the enthalpy of formation. The detonation performances were estimated with Kamlet-Jacobs equations based on the predicted density and enthalpy of formation in the solid state. ADAAF was also calculated by the same method for comparison. It was found that the nitramino group of ADNAAF can elongate the length of adjacent C-N bonds than the amino group of ADAAF. The gas-phase and solid-phase enthalpies of formation of ADNAAF are larger than those of ADAAF. The detonation performances of ADNAAF are better than ADAAF and RDX, and similar to HMX. The trigger bond of ADNAAF is the N-N bonds in the nitramino groups, and the nitramino group is more active than the amino group (-NH2).

Thermally stable energetic salts based on 3-nitramino-4-tetrazolefurazan

The combination of nitramino group and tetrazole with the furazan ring gave rise to energetic salts which are thermally stable up to 284 °C.

ChemInform Abstract: Synthesis of 3‐Nitramino‐4‐(1H‐1,2,3‐triazol‐1‐yl)‐1,2,5‐oxadiazoles and Their Salts.

AbstractTriazolylfurazans bearing a primary nitramino group attached to the furazan ring, e.g. (II), are prepared for the first time.

A New Approach to the Application of Molecular Surface Electrostatic Potential in the Study of Detonation

AbstractIn a sample of 22 nitramines, the simplest features of surface electrostatic potentials (SEPs), their positive (VS,max) and negative (VS,min) extremes, are related to their detonation velocities, D, at maximal theoretical densities. The relationships between the VS,min and D values logically show the nitramino group as responsible for detonation initiation for these compounds. On the other hand, the VS,max values gave complicated relationships. As a criterion of the imbalance between the VS,max and VS,min extremes their sum was derived and used as a new simple characteristic of SEPs, VS,Σ. The VS,Σ values have close relationships with the D values and the corresponding relationships uniquely determine the nitramino grouping as a reactivity center for detonation of nitramines. This new criterion is shown to be the best SEP characteristic for the study of detonation initiation. In all the relationships mentioned in this study of nitramines, the increase in potentials and/or their sum correspond with an increase in the D values (energy content of molecules).

Synthesis of 3-nitramino-4-(1H-1,2,3-triazol-1-yl)-1,2,5-oxadiazoles and their salts

Nitration of 3-amino-4-(1H-1,2,3-triazol-1-yl)-1,2,5-oxadiazoles (3-amino-4-triazolylfurazans) with a mixture of NaNO3 and conc. H2SO4 gave for the first time triazolylfurazans with a primary nitramino group attached to the furazan ring. If the starting amino(triazolyl)-furazan contains an aromatic substituent, the latter also undergoes nitration under the conditions studied. Some of these nitramines were converted into salts (K, Na, and NH4).

2,4,6-Trimethyl-N-nitroaniline

In 2,4,6-trimethyl-N-nitro­aniline (alternatively called mesitylnitramine), C9H12N2O2, the primary nitramino group is planar with a short N—N bond and is nearly perpendicular to the aromatic ring. The methyl group located in the para position is disordered, each H atom having half-occupancy. The mol­ecules are linked together along the [100] axis by inter­molecular N—H⋯O hydrogen bonds.

Structure and properties of N-methyl-N-(4-pyridyl)-nitramine and 1,4-dihydro-1-methyl-4-nitriminopyridine

The molecular structure and spectral properties of N-methyl-N-(4-pyridyl)-nitramine (1) and 1,4-dihydro-1-methyl-4-nitriminopyridine (3) were investigated by the X-ray diffraction, FTIR, nuclear magnetic resonance (NMR) methods and DFT theoretical calculations. N-methyl-N-(4-pyridyl)-nitramine (1) crystallises in the orthorhombic Pbca space group. It is composed of two planar fragments; nitramino (N2O2) group and the pirydyl ring. These two groups are twisted at about 70° with respect to each other, along the Ar–N bond. On the contrary, in compound 3, they are coplanar to each other. Twist of the nitramino group in 1 with respect to the pirydyl ring leads to a significant increase in C–N bond length ca. 0.07Å in comparison to the analogous bond in the nitrimine 3. The true nitramines, like 1, give strong bands in the infrared spectra, in the regions 1252–1276 and 1488–1563cm−1. In the spectra of nitrimine 3, the frequencies characteristic of the N-nitro group, appear at 1245–1255 and 1420–1450cm−1. The proton and carbon NMR spectra of 3 indicate that the ortho positions of the ring, in the liquid state, are magnetically equivalent, due to the fast rotation along the CN bond, which was formally a double bond. The nitramine 1 rearranges to 4-(N-methylamino)-3-nitropyridine, in 95% sulphuric acid, whereas the nitrimine 3 cannot rearrange in any way. The difference in the susceptibility towards rearrangement was explained by the electron deficient character of the migration terminus, i.e. the pyridine ring (3a).

Acidity and basicity of primary N‐phenylnitramines: catalytic effect of protons on the nitramine rearrangement

AbstractPara‐substituted N‐phenylnitramines were prepared either by oxidation of diazonium salts or by nitration under alkaline or acidic conditions. Isotopic [15N‐NO2] labelling indicated that the bands characteristic of the N‐nitro group appear in the 1318–1323 and 1585–1607 cm−1 regions. In the nitrogen NMR spectra, the nitramino group gives two resonances at −193 ± 3 (NH) and −32 ± 3 ppm (NO2). The chemical shifts in proton and carbon NMR spectra are predictable, based on increments and the additivity rule. The spectral data indicate the lack of conjugation between the nitramino group and another substituent bound to the ring. It seems to contradict the well‐known fact that substituents strongly (ρ = 4) influence the rate of nitramine rearrangement. The acidities of primary N‐phenylnitramines (3.77 < pKA < 5.62) are similar to those of benzoic acids and weakly dependent (ρ = 1) on the electronic character of a substituent. Based on the analogy with benzoic acids, it has been calculated that basicities of nitramines (pKB ≈ 21) are extremely low. Consequently, addition of protons to an intact nitramine molecule, as the preliminary step of the rearrangement, seems to be improbable. Migration of the N‐nitro group precedes protonation; the latter process facilitates transformation of intermediates into stable final products. Copyright © 2001 John Wiley & Sons, Ltd.

1-methyl-4-nitraminopyridinium nitrate and 4-nitraminopyridinium methanesulfonate.

In the title compounds, C6H8N3O2+*NO3- and C5H6N3O2+*-CH3SO3-, respectively, the cations are almost planar; the twist of the nitramino group about the C-N and N-N bonds does not exceed 10 degrees. The deviations from coplanarity are accounted for by intermolecular N-H...O interactions. The coplanarity of the NHNO2 group and the phenyl ring leads to the deformation of the nitramino group. The C-N-N angle and one C-C-N angle at the junction of the phenyl ring and the nitramino group are increased from 120 degrees by ca 6 degrees, whereas the other junction C-C-N angle is decreased by ca 5 degrees. Within the nitro group, the O-N-O angle is increased by ca 5 degrees and one O-N-N angle is decreased by ca 5 degrees, whereas the other O-N-N angle remains almost unchanged. The cations are connected to the anions by relatively strong N-H...O hydrogen bonds [shortest H.O separations 1.77 (2)-1.81 (3) A] and much weaker C-H...O hydrogen bonds [H...O separations 2.30 (2)-2.63 (3) A].

1-Nitroindoline.

In the title compound, C(8)H(8)N(2)O(2), the nitramino group is planar and only slightly twisted with respect to the indoline rings. The bridgehead N--C bond is slightly shorter than in typical secondary aromatic nitramines. The N--N bond has some double-bond character. The molecules are connected by weak C--H...O hydrogen bonds, forming chains parallel to the z direction.

Structure of N,4-dinitroaniline and its complex with sulfolane at 85 K; on the proton donor-acceptor affinity of the primary nitramine (HNNO2) group.

The NNO2 group of the title compound is significantly less twisted with respect to the aromatic ring in comparison to a typical secondary nitramine. The amide nitrogen is trigonally hybridized. The nitramino group is almost planar. The C-C-N-N torsion angles vary between ca 13 and 42 degrees, whereas the twist along the N-N bond is much smaller and amounts to between ca 1 and 15 degrees. Those twist angles are governed by a crystal packing and are much larger in the case of crystals of pure N,4-dinitroaniline in comparison to that of its complex with sulfolane. The deviations of the internal angles of the aromatic ring from 120 degrees do not exceed 3 degrees. The presence of the nitro group increases the C-C-C valence angle of ca 2.0-2.6 degrees, whereas an analogous effect associated with the nitramino group is much smaller (ca 0.3-1.3 degrees), pointing to its weak electron-withdrawing properties. The nitramino group displays no tendency to conjugate with an electron-demanding substituent across the ring. It participates in hydrogen bonding only as a hydrogen-bonding donor. It does not act as a proton acceptor, despite the fact that nitramine rearrangement is catalysed by acids.

Structure and properties of some nitro derivatives of N-methyl-N-phenylnitramine

Ten mono-, di- and tri-nitro derivatives of N-methyl-N-phenylnitramine were prepared and investigated using spectral and electrooptical methods. Three of them, viz. N-(2, 5-dinitrophenyl)-N-methylnitramine (monoclinic, P21/c, a=8.248(2), b=11.655(2), c=10.404(2)Å,β=102.57(2)°), N-(2,3-dinitrophenyl)-N-methylnitramine (monoclinic, P21/c, a=9.224(2), b=7.222(2), c=15.458(4)Å,β=101.08(2)°)) and N-(3,5-dinitrophenyl)-N-methylnitramine (monoclinic, P21/n, a=9.814(2), b=12.000(2), c=8.865(2)Å,β=114.94(2)°) were examined by the X-ray diffraction method. The nitramino group is nearly planar with the short N(7)–N(8) bond and strongly electron deficient N(8) atom. The nitramino group is twisted vs. the aromatic ring, there is no conjugation between the nitro and nitramino groups across the ring. The nitramino group is an electron withdrawing substituent due to the inductive effect. The number and positions of the Ar-nitro groups have no influence on the N-nitro group. Its migration ability cannot be explained in terms of the interaction between the migration origin and the ring substituents.

Molecular Dipole Moment and Interaction Dipole Moment in 2-N-Substituted Amino-3(or 5)-methyl-4-nitropyridines and Their N-Oxides

The dipole moments of 2-alkylaminoand 2-alkylnitramino-3(or 5)-methyl-4-nitropyridines and their N-oxides have been measured, as well as calculated, using vectorial summation of the group moments and by ab initio method. The estimated interaction dipole moments, μint, have been discussed in terms of the electronic and steric effects and intramolecular hydrogen bonding. Introduction of the NHCH3 group to position 2 in 4-nitropyridine strengthens the conjugation between the nitro group and ring nitrogen. The lack of such strengthening in 4-nitropyridine-N-oxides is explained as being due to formation of intramolecular hydrogen bond between the N-oxide group and the hydrogen of alkylamino group. Introduction of the nitramino group does not lead to marked modification of the charge distribution in a molecule. This fact may be explained by much weaker electron-donating ability of this group in comparison with the alkylamino group.

4-(N-Methylnitramino)pyridine 1-oxide

In the title compound, C 6 H 7 N 3 O 3 , the NNO 2 group is twisted ca 59° from the planar pyridine ring. The nitramino group is almost planar, with the N7 atom diverging 0.15 A from the C4-N8-C11 plane. The lone pair on N7 is included into the N-nitro group π-electron system resulting in two independent sets of multicenter π-orbitals. Significant anisotropy of the temperature dependence of thermal expansion is observed in the range 90-300 K.

1-Methyl-4-(N-methylnitramino)pyridinium bromide

The structure of the title compound, C 7 H 10 N 3 O 2 + .Br - , is composed of 1-methyl-4-(N-methylnitramino)pyridinium cations and bromide anions, with normal electrostatic interactions. The cations are present in the nitramino form. The N-NO 2 nitramino group is twisted 51.5(4)° out of the plane of the aromatic ring.

Crystal structure of bis(2,2-dinitropropyl)-nitramine (BDNPN)

A single-crystal X-ray diffraction study substantiated that the target oxidizer molecule bis(2,2-dinitropropyl)-nitramine (BDNPN) had been synthesized. BDNPN crystallizes in the monoclinic space group C2 with unit-cell dimensions a = 10.726(4) A, b = 5.922(3) A, c = 10.400(4) A, β = 110.01(3)°, with Z = 2 and a density of 1.72g/cm 3 . There are two molecules per unit cell which are approximately oriented along the c direction. The molecule contains two gem-dinitro groups and one planar nitramino group.

Multinuclear magnetic resonance and x‐ray diffraction studies of aminonitropyridines

AbstractThe 15N NMR spectra for 21 aminonitropyridines were measured and their chemical shifts assigned. The 1H and 13C NMR chemical shifts and spin–spin coupling constants were also determined for 16 compounds of this series. In order to relate the structural properties of nitramino groups and their 15N NMR chemical shifts in 2‐ and 4‐nitramino‐3‐nitropyridines, which differ remarkably from all other amino groups studied, low‐temperature 1H NMR, 17O NMR, comparative INEPT and IR spectroscopic studies were carried out. In addition, the x‐ray crystal structure of 2‐nitramino‐3‐nitropyridine was determined. Comparative spectroscopic studies showed that the nitramino derivatives exhibit different characteristics to the other compounds studied. Based on the x‐ray structural data, the nitramino group differs markedly from separate aryl‐bound amino and nitro groups. The nitramino group does not exhibit prototropic tautomerism in the crystalline state. This is in agreement with the small variation in the 15N NMR chemical shifts of the pyridine nitrogen, which excludes the prevalence of pyridinium ions. Among the four NMR nuclei studied, 15N seems to possess the best predictive power regarding the exceptional properties of the nitramino group.