One step synthesis of nitrogen-rich green primary explosives from secondary explosives: synthesis, characterization, and performance study

Abstract

Primary explosives are essential for initiating combustion or detonation in propellants and secondary explosives. Hence, there is a critical need to find a green and safe alternative primary explosive to replace the extremely toxic metal-based compounds. We have synthesized metal-free primary explosives and characterized them using various analytical techniques such as multi-nuclear magnetic resonance (NMR; ¹H, ¹³C, ¹⁵N), infrared spectroscopy (IR), elemental analysis (EA), high-resolution mass spectrometry (HRMS) and differential scanning calorimetry (DSC). The structure of 5,5′-diazido-4,4′-dinitro-1H,1′H-2,2′-biimidazole (6) was further supported by single crystal X-ray data. 5-Azido-4,4′,5′-trinitro-1H,1′H-2,2′-biimidazole (2) and dihydroxylammonium-5-azido-4,4′,5′-trinitro-[2,2′-biimidazole]-1,1′-diide (3) show excellent thermal stabilities (252 and 245 °C) and detonation velocities (8093 and 8494 m s⁻¹) compared to diazodinitrophenol (DDNP, 6900 m s⁻¹) and Pb(N₃)₂ (5877 m s⁻¹). Both compounds 2 and 3 are more insensitive to friction (>240 N) and impact sensitivity (5 to 10 J) than the benchmark materials DDNP (1 J, 24.7 N) and Pb(N₃)₂ (2.5 J, 0.1 N). Considering the overall fine-tuned performance, these newly synthesized compounds have significant potential to serve as primary explosives.