Davin G. Piercey

Nitrotetrazolate-2N-oxides and the Strategy of N-Oxide Introduction

The first anionic tetrazole-2N-oxide has been prepared by mild aqueous oxidation of easily prepared 5-nitrotetrazole with commercially available oxone in high yields. The result of protonating 5-nitrotetrazolate-2N-oxide has been identified as a hydroxytetrazole, and the nitrogen-rich salts including ammonium, hydroxylammonium, guanidinium, aminoguanidinum, diaminoguanidinium, and triaminoguanidinium have been prepared and characterized. When compared to the nitrogen-rich salts of nitrotetrazole, the nitrogen-rich salts of nitrotetrazole-2N-oxide show superior energetic performance as calculated by the EXPLO5 computer code, using heats of formation calculated using the CBS-4M level of quantum mechanical theory. The impact, friction, and electrical spark sensitivities of the nitrogen-rich nitrotetrazolate-2N-oxides were measured and cover the whole range from sensitive to insensitive energetic materials.

1,3-Bis(nitroimido)-1,2,3-triazolate Anion, the N-Nitroimide Moiety, and the Strategy of Alternating Positive and Negative Charges in the Design of Energetic Materials

This unique study reports on the 1,3-bis(nitroimido)-1,2,3-triazolate anion. This compound provides unique insight into both academic and practical considerations surrounding high-nitrogen systems. The bonding in this energetic anion can be represented multiple ways, one of which includes a chain of alternating positive/negative charges nine atoms long. The validity of this resonance structure is discussed in terms of experimental, computational, and valence bond results. The prepared materials based on this energetic anion were also characterized chemically (infrared, Raman, NMR, X-ray) and as high explosives in terms of their energetic performances (detonation velocity, pressure, etc.) and sensitivities (impact, friction, electrostatic), and the 1,3-bis(nitroimido)-1,2,3-triazolate anion is found to be very high performing with high thermal stabilities while being quite sensitive to mechanical stimuli.

The taming of CN7(-): the azidotetrazolate 2-oxide anion.

The highly sensitive 5-azidotetrazolate anion was oxidized to its corresponding N-oxide by aqueous oxidation in a buffered oxone solution to the azidotetrazolate 2-oxide anion. After acidic extraction and neutralization with ammonia, the ammonium salt was isolated. Several energetic salts of this novel anion were prepared from the ammonium salt, and in all cases were found to be of lower sensitivity than the corresponding 5-azidotetrazolate salt while still being highly sensitive towards mechanical stimuli. Explosive performances (detonation velocity, detonation pressure) of applicable salts were also found to be higher than the non-N-oxide variants. Preparation of the free acid 2-hydroxy-5-azidotetrazole was achieved by protonation of the anion and identified by NMR spectroscopy, whereas the majority of the azidotetrazolate 2-oxide salts have unequivocal crystallographic proof.

A Study of Cyanotetrazole Oxides and Derivatives thereof

In this work we report on the syntheses of energetic salts of cyanotetrazolate-1- and -2-oxides; this offers a unique ability to compare the effects of tetrazole 1- versus 2-oxidation. 5-Cyanotetrazolate-2-oxide can be synthesized by oxidation of the 5-cyanotetrazolate anion with Oxone, while the corresponding 1-oxide was synthesized by the rearrangement of azidoaminofurazan. Both chemical (multinuclear NMR, IR, and Raman spectroscopies, mass spectrometry, etc.) as well as explosive (impact, friction, and static sensitivities) properties are reported for these energetic salts. Calculated explosive performances using the EXPLO5 computer code are also reported. We furthermore detail the chemistry of these two anions, and their ability to form tetrazole-carboxamides, dihydrotetrazines, and tetrazines. The ability to hydrolyze cyanotetrazole oxides to their amides was demonstrated by two copper complexes. Several crystal structures of these species are presented in addition to full chemical characterization. Finally, the unique 1,4,-bis(2-N-oxidotetrazolate)-1,2,4,5-tetrazine anion was characterized as an energetic material as its ammonium salt.

An Energetic Triazolo-1,2,4-Triazine and its N-Oxide

The reaction of 3-amino-5-nitro-1,2,4-triazole with nitrous acid produces the corresponding diazonium salt. When the diazonium salt is treated with nitroacetonitrile, a subsequent condensation and cyclization reaction occurres to produced 4-amino-3,7-dinitrotriazolo-[5,1-c][1,2,4] triazine (DPX-26). X-ray crystallographic analysis shows that the DPX-26 has a density of 1.86 g cm-3 , while it is calculated to have a heat of formation of 398.3 kJ mol-1 . DPX-26 is predicted to approach the explosive performance of RDX but displays significantly better safety properties. Oxidation of DPX-26 using hypofluorous acid produces 4-amino-3,7-dinitrotriazolo-[5,1-c][1,2,4] triazine 4-oxide (DPX-27), which is also predicted to be a high-performance material with enhanced safety properties.

Copper Salts of Halo Tetrazoles: Laser-Ignitable Primary Explosives

Syntheses of the primary explosives copper (II) 5-chlorotetrazolate and copper (II) bromotetrazolate are described. The physical and thermal stabilities of both compounds were determined, and their explosive ability was characterized. Additionally, the first reported X-ray structure of a 5-chlorotetrazole is reported.

Reaction of Copper(I) Nitrotetrazolate (DBX-1) with Sodium m-Periodate

The reaction of the lead-free primary explosive copper(I) 5-nitrotetrazolate (DBX-1) with sodium m-periodate yields a green precipitate of copper(II) iodate. The energetic properties of the copper(I) nitrotetrazolate starting material are lost since the nitrotetrazolate is removed into the aqueous phase during rinsing, leaving only non-explosive copper(II) iodate and copper(II) periodate. Based on the results of this investigation, the use of oxidizing components in DBX-1 formulations may be limited due to the readiness of copper(I) to be oxidized to copper(II). Graphical Abstract Reaction of Copper(I) Nitrotetrazolate (DBX-1) with Sodium m-Periodate