1-Amino-1-hydrazino-2,2-dinitroethene and corresponding salts: synthesis, characterization, and thermolysis studies.

Synthesis, characterization, and thermolysis studies of 1-amino-1-hydrazino-2,2-dinitroethene (2) and salts thereof are reported. These compounds have been fully characterized by IR and NMR spectroscopy, elemental analysis, differential scanning calorimetry (DSC), density, and impact sensitivity measurements. Compound 2 decomposes at 124.5 °C (DSC) and the salts decompose over the range 138.6-181.6 °C, thus showing higher thermostability. The calculated detonation pressures (P) for these salts range from 27.2 to 37.8 GPa, and detonation velocities (vD) fall between 8424 to 9482 m s(-1); these properties make them competitive energetic materials.

Ionic liquids as hypergolic fuels.

In propellant systems, fuels of choice continue to be hydrazine and its derivatives, even though they comprise a class of acutely carcinogenic and toxic substances which exhibit rather high vapor pressures and require expensive handling procedures and costly safety precautions. Only recently (2008), ionic liquids (salts with melting points less than 100 °C) with the dicyanamide anion were shown to exhibit hypergolic properties (instantaneous ignition when contacted with oxidizers (100 % nitric acid, WFNA)). Such liquids tend to have low volatilities, and high thermal and chemical stabilities, and often exhibit long liquid ranges which could allow utilization of these substances as bipropellant fuels over a variety of conditions. A new family of dicyanoborates is presented, which can be synthesized in water, with substituted N-acyclic, N-cyclic, and azolium cations has met nearly all of the desired important criteria needed for well-performing fuels.

Nitroimino-tetrazolates and oxy-nitroimino-tetrazolates.

Highly energetic 1,1'-ethylenebis(oxy)bis(5-nitroimino-tetrazolate) salts were obtained by reacting equimolar quantities of the acidic 1,1'-ethylenebis(oxy)bis(5-nitroimino-tetrazole) and energetic bases in aqueous solution. Additionally, metathesis of silver 1,1'-ethylenebis(oxy)bis(5-nitroimino-tetrazolate) with diaminoguanidinium chloride or triaminoguanidinium chloride gave the corresponding oxy-nitroimino-tetrazolate salt. These salts were fully characterized using IR and multinuclear NMR spectroscopy, elemental analysis, and differential scanning calorimetry (DSC), and, in some cases, 2·2H(2)O, 8·2H(2)O, 10, 13·2H(2)O and 14, with single crystal X-ray structuring. The heats of formation for all compounds were calculated with Gaussian 03 and then combined with measured densities to determine detonation pressures (P) and velocities (D) of the energetic materials (Cheetah 5.0). The impact sensitivities of all salts were found to be less than those of the parent compounds. The physical and detonation properties of these oxy-nitroimino-tetrazolate salts are comparable to the analogous newly prepared diaminoguanidinium and triaminoguanidinium 1,1'-ethylenebis(5-nitroimino-tetrazolate)s.

Taming of the silver FOX.

The first silver-FOX, silver-ammonia-FOX, and silver-amine-FOX compounds were synthesized by the reactions of silver nitrate with K-FOX or guanidine-FOX in water, aqueous ammonia, and amines, respectively. The crystal structure of silver-ammonia-FOX exhibits unique covalent bonding behavior, which is supported by NBO calculations.

3,4,5-Trinitropyrazole-based energetic salts.

High-density energetic salts that are comprised of nitrogen-rich cations and the 3,4,5-trinitropyrazolate anion were synthesized in high yield by neutralization or metathesis reactions. The resulting salts were fully characterized by (1)H, (13)C NMR, and IR spectroscopy; differential scanning calorimetry; and elemental analysis. Additionally, the structures of the 3,5-diaminotriazolium and triaminoguanidinium 3,4,5-trinitropyrazolates were confirmed by single-crystal X-ray diffraction. Based on the measured densities and calculated heats of formation, the detonation performances (pressure: 23.74-31.89 GPa; velocity: 7586-8543 ms(-1); Cheetah 5.0) of the 3,4,5-trinitropyrazolate salts are comparable with 1,3,5-triamino-2,4,6-trinitrobenzene (TATB; 31.15 GPa and 8114 ms(-1)). Impact sensitivities were determined to be no less than 35 J by hammer tests, which places these salts in the insensitive class.

Hypergolic N,N-dimethylhydrazinium ionic liquids.

N,N-Dimethylhydrazinium dicyanamide and nitrocyanamide ionic liquids (ILs) were prepared by quaterization of N,N-dimethylhydrazine with alkyl halides followed by metathesis reactions with silver dicyanamide or silver nitrocyanamide. The key physicochemical properties, such as melting point and decomposition temperatures, density, viscosity, heat of formation, detonation pressure and velocity, and specific impulse were measured/calculated. The impact of anions and alkyl-substituted cations on these properties is demonstrated. Droplet tests with white-fuming nitric acid (WFNA) as an oxidizer were utilized to show that the 14 new N,N-dimethylhydrazinium salts are hypergolic with ignition delay (ID) times ranging from 22 to 1642 ms, thereby suggesting that some may have potential as bipropellants.

Inorganic or organic azide-containing hypergolic ionic liquids.

Recently extensive research has focused on replacing toxic hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine as liquid propellant fuels. 2-Azido-N,N-dimethylethylamine (1) is a good candidate to replace hydrazine derivatives in certain hypergolic fuel applications. Energetic ionic liquids that contain the 2-azido-N,N,N-trimethylethylammonium cation with nitrocyanamide, dicyanamide, dinitramide, or azide anion have been successfully synthesized in good yields by metathesis reactions. Ionic liquids have received considerable attention as energetic materials. The replacement of hydrazine with tertiary ammonium salts is especially attractive since many ionic liquids are models for green chemistry. In this work, new azide-functionalized ionic liquids are demonstrated to exhibit hypergolic activity with such oxidizers as 100% nitric acid or nitrogen tetraoxide (NTO).

Energetic ethylene- and propylene-bridged bis(nitroiminotetrazolate) salts.

High energy density materials with ethylene- and propylene bis(5-nitroiminotetrazolate) as the anions are reported; all salts were fully characterized by IR, and (1)H, (13)C, and (15)N NMR spectroscopy as well as elemental analyses. In addition, the heats of formation (DeltaH(f)) and the detonation pressures (P) and velocities (D) were calculated.The synthesis and detonation properties of high energy density materials with ethylene- and propylene bis(nitroiminotetrazolate) as the anions are reported; all salts were fully characterized by IR, and (1)H, (13)C, and (15)N NMR spectroscopy as well as elemental analyses. In addition, the heats of formation (DeltaH(f)) were calculated with the Gaussian 3.0 suite of programs. By using the experimental values for the densities of the nitroiminotetrazolate salts, the detonation pressures (P) and velocities (D) were calculated using Cheetah 5.0.

Carbonyl and oxalyl bridged bis(1,5-diaminotetrazole)-based energetic salts.

High density energetic salts containing nitrogen rich cations and carbonyl- or oxalylbis(diamino-tetrazole) anions, which were obtained from cyanogen azide and hydrazine, were readily synthesized. In every case, a new family of energetic salts 3-14 were characterized by vibrational spectroscopy, multinuclear ((1)H, (13)C, (15)N) NMR, elemental analyses, density, differential scanning calorimetry and impact sensitivity. Compound 12 was structured by single crystal X-ray diffraction. The densities of 3-14, determined by gas pycnometer, range between 1.500 and 1.676 g cm(-3). The heats of formation and detonation properties for these stable salts were calculated by using Gaussian 03 and Cheetah 5.0, respectively.

Disubstituted azidotetrazoles as energetic compounds.

Base-catalyzed activation of the C--F bond in the trifluoromethylazo-substituted cyclic and acyclic alkanes provides a route to disubstituted azidotetrazoles. For example, the reaction of 1,2-bis(trifluoromethylazo)ethane with four equivalents of NaN(3) gave the alkyl-bridged bis(5-azido-1H-tetrazol-1-yl)-1,2-dimine, N,N'-bis(5-azido-1H-tetrazol-1-yl)-1,2-diiminoethane, in 75 % yield (see scheme).Disubstituted azidotetrazoles are synthesized by the base-catalyzed activation of the C--F bond in the trifluoromethylazo-substituted cyclic and acyclic alkanes. From the reaction of trans-1,4-bis(trifluoromethylazo)cyclohexane with four equivalents of NaN(3), N,N'-bis(5-azido-1H-tetrazol-1-yl)-1,4-diiminocyclohexane was formed in good yield. While, from the similar reaction using cis/trans-1,2-bis(trifluoromethylazo)cyclohexane, (5-azido-1H-tetrazol-1-yl)-[6-(5-azido-1H-tetrazol-1-ylimino)cyclohexenyl]amine was formed as the principal product. The structure of these new disubstituted azidotetrazoles was determined by crystal structure analysis as well as NMR and IR spectroscopy. In a similar fashion, from three trifluoromethylazo-substituted acyclic alkanes, corresponding alkyl-bridged N,N'-bis(5-azido-1H-tetrazol-1-yl)diiminoalkanes were obtained. For example, from 1,2-bis(trifluoromethylazo)ethane, N,N'-bis(5-azido-1H-tetrazol-1-yl)-1,2-diiminoethane was obtained in 75 % yield. Heats of formation, detonation pressures, detonation velocities, and impact sensitivities are reported for these new disubstituted azidotetrazoles.

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.

Experimental and theoretical studies on some energetic functionalized trimethylamine derivatives.

The synthesis and structural properties (from X-ray diffraction or B3LYP/6-31G(d) calculations) of three energetic compounds derived from tris(chloromethyl)amine and of tris(chloromethyl)amine itself were investigated and compared to those of compounds with similar structures. The compounds have almost planar NC(3) units at their amine center, and the substituents bound to the CH(2) groups tend to be reactive towards further substitution. Multiple hyperconjugation was used to explain these observations.

1,3-Diazido-2-(azidomethyl)-2-propylammonium salts.

New energetic inorganic materials composed of 1,3-diazido-2-(azidomethyl)-2-propylammonium salts have been fully characterized by IR, (1)H, (13)C, and (15)N NMR spectroscopy and by elemental analyses, as well as single crystal X-ray diffraction. In addition, the heats of formation and detonation pressures and velocities were calculated.

Hypergolic ionic liquids with the 2,2-dialkyltriazanium cation.

No flame, no gain: A hypergolic mixture is composed of stable species that readily react/ignite on molecular contact. Both the anion and the cation in an ionic liquid play prominent roles in determining hypergolic properties as well as ignition delay times. With the 2,2-dialkyltriazanium cation, salts with nitrate, chloride, nitrocyanamide, and dicyanamide anions are hypergolic.