Synthesis and Characterization of N-methylene-C Bridged Pyrazole and Tetrazole based Energetic Compounds

Abstract

Properties of energetic compounds can be fine-tuned by linking pyrazole and tetrazole ring via N methylene-C-connection. The pyrazole moiety with multiple nitro groups provides good energy content, high thermal stability and low sensitivity, whereas, tetrazole moiety improves the heat of formation and nitrogen percentage. In this work, we have synthesized various compounds having N-methylene-C linked 4-hydroxy-3,5-dinitropyrazole and tetrazole moieties. Reaction of disodium salt of 3,4-dinitro-4-oxidopyrazole-1-ide with chloroacetonitrile resulted in N-acetonitrile derivative of 4-hydroxy-3,5-dinitropyrazole. Cyano moiety was further converted to tetrazole moiety using sodium azide and ammonium chloride to give target compound 16 having N methylene-C linked 4-hydroxy-3,5-dinitropyrazole and tetrazole moieties. In order to modify the physiochemical properties, compound 4 was further converted to energetic salts (17 and 18) by reaction with nitrogen rich bases. All the compounds were thoroughly characterized by IR, NMR [1 H, 13C{1 H}], elemental analysis, and differential scanning calorimetry (DSC).