Pushing the Energy-Sensitivity Balance with High-Performance Bifuroxans

Abstract

Several energy-rich bifuroxans incorporating nitro and azido functionalities have been synthesized and thoroughly characterized by IR and multinuclear NMR spectroscopy, elemental analyses, single-crystal X-ray diffraction, and differential scanning calorimetry. N-oxide regiochemistry was employed to design the tunable azido(nitro)bifuroxans with different physicochemical and energetic properties. All synthesized compounds have high enthalpies of formation (449−777 kJ mol −1 ) and attractive performances, as evidenced by the high detonation velocities (8.95−9.75 km s −1 ) and Champan−Jouguet pressures (35−45 GPa). The most powerful energetic material in this series is 4,4′-dinitro-3,3′-bifuroxan. This hydrogen-free molecule (C 4 N 6 O 8 ) exhibits an outstanding heat of explosion value of 15.3 kJ cm −1 , far exceeding the top energetic material hexanitrohexaazaisowurtzitane CL-20. At the same time, the impact and friction sensitivities of 4,4′-dinitro-3,3′-bifuroxan were deemed acceptable for practical use. Overall, 4,4′-dinitro-3,3′-bifuroxan breaks a general trend called the "energy-sensitivity rule", which describes a linear increase of the mechanical sensitivity with a growth of the energetic content of the molecule, and, thus, offers great promise for future applications.

Nitro-, Cyano-, and Methylfuroxans, and Their Bis-Derivatives: From Green Primary to Melt-Cast Explosives

“…Computational estimations of the detonation parameters were performed using the Pepekin–Lebedev empirical method [ 79 ]. This method is similar to the Kamlet approach, however, exhibits a better accuracy when compared with the available experimental data for the CHNO and CNO explosives (see more details in the Supporting Information of [ 21 ]).…”

“…We hypothesized these peaks to represent the thermal isomerization of 3-nitrofuroxans to the thermodynamically more preferable 4-nitro isomers. This reaction is known to occur at elevated temperatures (t > 100 • C) for a wide set of nitrofuroxans [10,[19][20][21]. The third thermal process tracked by DSC is the exothermal thermal decomposition.…”

“…The overall accuracy of these methods on a test set composed of nitrogen-rich heterocyclic compounds turned out to be close to "chemical" (~4 kJ mol −1 ). Thus, we commenced the study of the gas-phase thermochemistry of the furoxan derivatives 1-20 from the multilevel calculations of atomization energies for furoxan (21), its hypothetical mononitro derivatives 22 and 23, and several related heterocyclic frameworks (3,3′-and 4,4′-bisfuroxans 24 and 25, as well as 3,3′-and 4,4′-azobisfuroxans 26 and 27, Chart 4). The most reliable W2-F12 formation enthalpies for 21-27 are listed in Table 1.…”

“…Among a variety of energetic patterns considered for further functionalization, the 1,2,5-oxadiazole-2-oxide (often referred to as furoxan) ring is indeed prominent due to its attractive oxygen balance, high density of energetic derivatives, and high positive enthalpy of formation [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. Although only two positions in the furoxan ring are available for the introduction of energetic substituents, the N -oxide regioisomerism is a promising strategy for tuning the detonation performance of furoxan-based energetic materials [ 19 , 20 , 21 , 22 ].…”

“…A similar idea of a combination of two highly energetic nitrofuroxan moieties has recently been implemented yielding an extremely powerful bisnitrofuroxan [21,34]. In the present study, we consider in detail the important methylfuroxan and nitrofuroxan structural motifs as functional explosophoric building blocks in the design of multipurpose energetic materials (Figure 2).…”