Simple methods for the introduction of nitrate ester, amino and diazo-oxide substituents into dinitromethylpyrazole

Abstract

The precursor 3,5-dinitro-4-chloro-1-(dinitromethyl)pyrazole (A) was synthesized by a two-step reaction with a yield of 81.5%. Nitrate ester, amino and diazo-oxide groups were introduced to A by the one-step substitution of the chlorine group in water. This method provides the possibility for large-scale preparation due to its simplicity and efficiency. The reaction mechanisms were explained by density functional theory. Among these compounds, the hydroxylamine salt B2 exhibits high detonation performance (P = 35.5 GPa; v_D = 8842 m s⁻¹) and oxygen balance (OB_CO = 27%), superior to those of ADN (P = 23.6 GPa; v_D = 7860 m s⁻¹; OB_CO = 25.7%), and has a promising future as an energetic oxidant. The diazo-oxide zwitterion C1 possesses good detonation performance (P = 37.7 GPa; v_D = 9159 m s⁻¹), higher than that of RDX (P = 34.9 GPa; v_D = 8795 m s⁻¹), and features a comparable impact sensitivity with DDNP (IS = 1 J), which make it a promising candidate for green primary explosives. Based on the good reactivity towards nucleophiles of the chlorine group, this is a simple method to introduce substituents into dinitromethylpyrazoles to tune their oxygen balance and detonation performance.