Connecting energetic nitropyrazole and aminotetrazole moieties with N,N′-ethylene bridges: A promising approach for fine tuning energetic properties

Abstract

A new approach for fine tuning the properties of energetic compounds through bonding of energetic pyrazoles with tetrazole moieties by means of N,N′-ethylene bridges is described. Reactions of various pyrazole derivatives with 2-haloethylamines, followed by reaction with cyanogen azide resulted in the formation of compounds having ethylene-bridged 5-aminotetrazole and nitropyrazole. Further reactions on this basic framework resulted in various energetic compounds having mono, di or tri nitro-substituted pyrazole moieties, and an amino or nitroimino-substituted tetrazole ring. All the compounds were thoroughly characterized by IR, and NMR [¹H, ¹³C{¹H}, ¹⁵N] spectra, elemental analysis, and differential scanning calorimetry (DSC). Some of them were also structurally characterized with single-crystal X-ray diffraction studies. Heats of formation and detonation performance for all the energetic compounds were calculated using Gaussian 03 and EXPLO5 v6.01 programs, respectively. Initial studies showed that the properties of energetic compounds can indeed be fine-tuned by careful selection of the number and nature of energetic groups on the pyrazole and tetrazole rings.