An Improved Safe Method for the Synthesis of Ammonium 5-Nitrotetrazolate (ANT), a Key Intermediate for the Synthesis of Green Energetic Materials (GEMs)

Ammonium 5-nitrotetrazolate (ANT) is an important precursor for the synthesis of green energetic materials (GEMs), including lead/mercury-free environmentally benign primary explosives. The currently employed methods for the synthesis of ANT are hazardous, use an excess of organic solvents/reagents and thus generate effluent. Furthermore, these methods offer low yields of ANT as they involve multistep processes. We describe herein an improved, safe and convenient method for the synthesis of ANT, which greatly improves the process safety and product yield. The advantage of this method is that it avoids hazardous operations, such as the isolation and handling of acidic copper(II) nitrotetrazolate, an extremely sensitive explosive intermediate during the preparation of ANT. In our procedure, 5-aminotetrazole (5-AT) is diazotized with sodium nitrite and nitric acid in the presence of a copper salt. The sensitive copper acid salt thus formed from the reaction mixture is treated in situ with aqueous barium hydroxide to convert it to barium 5-nitrotetrazolate and insoluble copper oxide. Finally, the aqueous barium 5-nitro-1H-tetrazolate (BaNT) is treated with ammonium sulfate to yield ammonium 5-nitrotetrazolate (ANT) in good yield. The synthesized ANT was characterized by its physicochemical properties using spectral and thermal techniques. The purity of the ANT was measured by HPLC and ion chromatography (IC). Furthermore, the structure of ANT was confirmed by single crystal X-ray analysis.