Guo-Hong Tao

Nitrocyanamide‐Based Ionic Liquids and Their Potential Applications as Hypergolic Fuels

Nitrocyanamide ionic liquids with substituted imidazolium, guanidinium, and tetrazolium cations have been synthesized and fully characterized. Aminoguanidinium nitrocyanamide (7) crystallizes in the triclinic system P1. The results obtained from theoretical calculations based on 7 are consistent with the single-crystal structure data. These ionic liquids exhibit desirable physicochemical properties, such as low melting points and good thermal stabilities. Furthermore, they are all impact insensitive materials. Their energetic performances, including heats of formation, detonation pressures, and detonation velocities, were studied by a combination of theoretical and empirical calculations. The ionic liquids 1-4 have large liquid ranges and low viscosities. They were shown to be promising candidates as hypergolic ionic liquids through the combustion tests with 100% HNO(3).

Energetic nitrogen-rich salts and ionic liquids: 5-aminotetrazole (AT) as a weak acid

5-Aminotetrazole (AT) behaves as a weak acid and can be used to obtain nitrogen-rich energetic salts and ionic liquids. These AT salts have been characterized by IR, NMR, elemental analysis, thermal stability, phase behavior, and density. The salt 2 contains 82% nitrogen, and 7 has the highest nitrogen content (68%) of any known room temperature ionic liquid. Compound 5 crystallizes in the chiral orthorhombic system P2(1)2(1)2(1). Based on their calculated heats of formation, detonation properties, and thermal and hydrolytic stabilities, these stable AT compounds hold promise for energetic applications.

Energetic 1,5-diamino-4H-tetrazolium nitro-substituted azolates

1,5-Diaminotetrazole (DAT) is a fascinating component in the construction of high-energy-density materials because of its extremely high nitrogen content (∼84%). Three DAT nitro-substituted azolate salts were synthesized and fully characterized by IR, NMR, elemental analysis, thermal stability, phase behavior, and density. 1,5-Diamino-4H-tetrazolium 5-nitrotetrazolate salt (2) crystallizes in the orthorhombic system Pbca. The detonation pressure (P) values calculated for these salts range from 28.05 to 29.88 GPa, and the detonation velocities (D) from 8343 to 8655 m s−1, which make them competitive energetic materials. Each of the compounds has an oxygen balance approaching zero (−23.8 to −33.5%). Their impact sensitivities were determined. The salts were compared using natural bond orbital (NBO) analysis of the nitro-substituted azolate anions. These CHNO-explosives, DAT nitro-substituted azolate salts, are potential green energetic materials which are obtained via a straightforward synthetic route.

Energetic Ionic Liquids based on Lanthanide Nitrate Complex Anions

Energetic ionic liquids based on anionic lanthanide nitrate complexes Cat(+) (3)[Ln(NO(3))(6)](3-), where Cat(+) is guanidinium, 4-aminotriazolium, 4-amino-1-methyltriazolium, 4-amino-1-ethyltriazolium, 4-amino-1-butyltriazolium, 1,5-diaminotetrazolium, and 1,5-diamino-4-methyltetrazolium, were prepared. The hexanitratolanthanate (-cerate) salts with the last two cations, which are the first CO-balanced energetic ionic liquids that are stable to hydrolysis and air, have impact sensitivities of about 27 J. These ionic liquids were obtained by an environmentally friendly, simple method using nitrate-containing precursors. All salts were fully characterized by IR and NMR spectroscopy, elemental analysis, and determination of thermal stability, phase behavior, density, and water content. According to theoretical calculations, these new compounds have potential as propellants.

Activation of the C-F Bond : Transformation of CF3N=N-into 5-Azidotetrazoles

Considerable attention in recent years has been directed toward the synthesis of energetic heterocyclic compounds including the syntheses and applications of new energetic tetrazole derivatives. Recently, many kinds of energetic tetrazole compounds, some of which contained substituents such as azide groups, were reported. The development of new synthetic routes towards energetic compounds continues to be a topic of significant interest in synthetic chemistry. Many papers have dealt with the preparation of 5-azidotetrazoles. Nearly 70 years ago, 5-azidotetrazole and sodium 5-azidotetrazolate were prepared by the reaction of cyanogen halide (ClCN or BrCN) with sodium or barium azide and acid (Scheme 1). Further detailed investigation on the syntheses and characterizations of 5-azidotetrazoles have been carried out.

A thermally stable nitrogen-rich energetic material—3,4,5-triamino-1-tetrazolyl-1,2,4-triazole (TATT)

The nitrogen-rich energetic material 3,4,5-triamino-1-tetrazolyl-1,2,4-triazole (TATT) was synthesized from diaminoguanidine using a straightforward method. The assumption that a 1,2,4-triazole ring is an intermediate in the one-pot reaction is supported by the synthesis of TATT from an analogous reaction of 3,4,5-triamino-1,2,4-triazole with cyanogen azide. TATT·HNO3 crystallizes in the monoclinic system P21/c. TATT has excellent thermal stability which resembles triaminotrinitrobenzene (TATB), but with a higher positive heat of formation and greater impact insensitivity.

5-(1,2,3-Triazol-1-yl)tetrazole derivatives of an azidotetrazole via click chemistry.

N-C bonded (non-bridged) 5-(1,2,3-triazol-1-yl)tetrazoles were synthesized by the Cu(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition click reaction using 5-azido-N-(propan-2-ylidene)-1H-tetrazole (1). For example, the click reaction of 1 in the presence of CuSO(4)5 H(2)O and Na ascorbate at 65-70 degrees C for 48 h in CH(3)CN/H(2)O co-solvent was found to be limited to only terminal alkynes that have electron-withdrawing groups, CF(3)C[triple chemical bond]CH (2 a) and SF(5)C[triple chemical bond]CH (2 b), giving rise to isopropylidene-[5-(4-trifluoromethyl-1,2,3-triazol-1-yl)tetrazol-1-yl]amine (3 a) and isopropylidene-[5-(4-pentafluorosulfanyl-1,2,3-triazol-1-yl)tetrazol-1-yl]amine (3 b) in 47 % and 66 % yields, respectively. When carried out under conditions using CuI and 2,6-lutidine as catalysts at 0 degrees C for 13 h in CHCl(3), the click reaction was versatile toward alkynes even those having electron-donating groups. Properties of new products were determined and compared with those of 1. Heats of formation, detonation pressures, detonation velocities and impact sensitivities are reported for these new 5-(1,2,3-triazol-1-yl)tetrazoles.

Slightly Viscous Amino Acid Ionic Liquids: Synthesis, Properties, and Calculations

Slightly viscous N-alkyl-substituted glycine ester ionic liquids were prepared via alkylation of glycine ethyl esters with appropriate haloalkanes followed by anion exchange with lithium bis(trifluoromethanesulfonyl)amide. These ionic liquids have been characterized by IR, NMR, elemental analysis, thermal stability, phase behavior, viscosity, and density. Compound 9 crystallizes in the monoclinic system, P2(1)/c. The viscosities of the N,N,N-trialkyl-substituted glycine ester ionic liquids (6, 8, 10) are in the approximately 200 to 400 cP range at 25 degrees C. While exhibiting liquid characteristics analogous to the traditional heterocyclic ionic liquids, these new liquids are much less viscous than known amino acid ionic liquids. The correlation of viscosity and temperature was determined. To understand the influence of the alkyl and ester-substituted groups on viscosity, the electronic distributions and the electrostatic potential surfaces of the glycine-based cations, including glycine (Gly(+)), glycine ethyl ester (GlyET(+)), N,N-dimethyl glycine (DMGly(+)), N,N-dimethyl glycine ethyl ester (DMGlyET(+)), N,N-dimethyl-N-propyl glycine ethyl ester (DMPGlyET(+)), N,N-dimethyl-N-3-fluoropropyl glycine ethyl ester (DMPFGlyET(+)), and N-butyl-N,N-dimethyl glycine ethyl ester (DMBGlyET(+)) cations have been investigated and analyzed. The possible effects on the viscosity coming from the intermolecular interactions arising from Coulomb interactions, hydrogen bonding, polarizability effects, and van der Waals interactions are considered.