Abstract
Pyridine derivatives based on the addition of trinitromethyl functional groups were synthesized by the reaction of N2O4 with the corresponding pyridinecarboxaldoximes, then they were converted into dinitromethylide hydrazinium salts. These energetic compounds were fully characterized by IR and NMR spectroscopy, elemental analysis, differential scanning calorimetry (DSC), and X-ray crystallography. These pyridine derivatives have good densities, positive enthalpies of formation, and acceptable sensitivity values. Theoretical calculations carried out using Gaussian 03 and EXPLO5 programs demonstrated good to excellent detonation velocities and pressures. Each of these compounds is superior in performance to TNT, while 2,6-bis(trinitromethyl)pyridine (D = 8700 m·s−1, P = 33.2 GPa) shows comparable detonation performance to that of RDX, but its thermal stability is too low, making it inferior to RDX.
Highlights
There are currently ongoing efforts to synthesize novel energetic materials with improved performance and decreased sensitivity [1,2,3,4,5,6]
Compared with the benzene ring, nitrogen-containing heterocycles typically possess a greater enthalpy of formation as well as a higher density and more positive oxygen balance [10,11], all of which are desirable characteristics for new energetic compounds
Based on a method reported in reaction of N2O4 with pyridine-2-carboxaldoxime (Scheme 1)
Summary
There are currently ongoing efforts to synthesize novel energetic materials with improved performance and decreased sensitivity [1,2,3,4,5,6]. These requirements are quite often mutually exclusive, such that the desired combination of high detonation performance with maximum possible chemical stability is a major challenge. Over the last few decades, several strategies for the design of energetic materials that have a high energy content in conjunction with good thermal and mechanical stabilities have been developed [7,8], one of which is to replace benzene rings with nitrogen-containing heterocycles as fundamental components of molecular structures [2,9]. Due to the electron deficient character of the azine ring, it is difficult to perform electrophilic aromatic substitution on the ring, so the introduction of nitro groups into azine rings remains a challenging task in practice
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