3,3′-Azobis(6-amino-1,2,4,5-tetrazine): A Novel High-Nitrogen Energetic Material

Abstract

The synthesis of compounds known as high-nitrogen energetic materials has been the focus of our group for the past decade. High-nitrogen compounds form a unique class of energetic materials deriving most of their energy from their very high positive heats of formation rather than from oxidation of the carbon backbone, as with traditional energetic materials.[1] The high nitrogen content typically leads to high densities, and the low amount of hydrogen and carbon also allows for a good oxygen balance to be achieved more easily; oxygen balance is a measure of the oxygen/fuel ratio in a compound. We have demonstrated that high-nitrogen materials can show remarkable insensitivity to electrostatic discharge, friction, and impact.One high-nitrogen system extensively studied by our group is the 1,2,4,5-tetrazine ring. We have synthesized several energetic 1,2,4,5-tetrazines having applications as propellants, explosives, and pyrotechnic ingredients.[2] In the pursuit of new high-nitrogen materials with novel properties, we have recently been studying azo-1,2,4,5-tetrazines.We became interested in the synthesis of azo-1,2,4,5-tetrazines from our previous studies on azo-1,2,5-oxadiazoles. We found that 327 kJ mol À1 of energy is gained in the transformation of 4,4'-hydrazobis-(1,2,5-oxadiazol-3-amine) to 4,4'-azobis(1,2,5-oxadiazol-3-amine) (Scheme 1). The latter material is a thermally stable, insensitive explosive.[3] Extrapolating from these data, 3,3'-azobis(6-amino-1,2,4,5-tetrazine)

Impact sensitivity and the maximum heat of detonation

“…For instance, a higher nitrogen/ carbon ratio in the molecular framework does increase the heat of formation and therefore Q max , but another result is often a greater density [39,40,43,48,66], since a nitrogen atom has a larger mass and smaller volume than the C-H that it typically replaces [67].…”

“…More than half of those in Table 1 are negative, including those for such well known explosives as PETN, FOX-7, picric acid, and TNT. (Acronyms are defined in Tables 1 and 2) In recent years, however, there has been a focus upon synthesizing compounds with increased nitrogen/carbon ratios in their molecular frameworks [3,29,[38][39][40][41][42][43][44] -which tends to result in higher, more positive heats of formation. Some examples are 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide, 1 (ΔH f = 48.02 kcal mol -1 [38]), 5-amino-3-nitro-1,2,4-triazole, 2 (ΔH f =61 kcal mol -1 [29]) and 3,3'-azo-bis(6-amino-1,2,4,5-tetrazine), 3 (ΔH f =206 kcal mol -1 [41] …”

Nitro Groups vs. N-Oxide Linkages: Effects Upon Some Key Determinants of Detonation Performance

“…Since a high N/C ratio in the molecular framework is expected to be accompanied by a more positive ΔH f,X and therefore larger Q, as well as possibly a greater ρ, there has been a growing interest in designing and synthesizing "high nitrogen" compounds as potential explosives [25,[30][31][32][33][34][35][36][37].…”

Molecular design of new nitramine explosives: 1,3,5,7-tetranitro-8-(nitromethyl)-4-imidazolino[4,5-b]4-imidazolino-[4,5-e] pyridine and its N-oxide

“…On the other hand, since the presence of N atom in the aromatic ring can increase the density effectively, e.g., the density of benzene is only 0.897 g·cm -3 , but that of pyridine is 0.982 g·cm -3 , the presence of pyridine in molecule is supposed to improve its density and correspondingly increases the detonation velocity and pressure [10]. Therefore, the search for new potential high-energy density materials containing pyridine has attracted many attentions [11][12][13][14][15][16][17][18][19][20][21]. In addition, studies show that introducing nitramine group (N-NO 2 ) into a molecule can improve its detonation performance, for example, there are 3, 4, and 6 N-NO 2 groups in hexahydro-1,3,5-Trinitro-1,3,5-triazine (RDX), HMX, and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL- 20) respectively, and their deto-nation performance increase in the same order.…”