3,3′‐Bi(1,2,4‐oxadiazoles) Featuring the Fluorodinitromethyl and Trinitromethyl Groups

Abstract

Here we report on the preparation of two hydrogen atom free 3,3'-bi(1,2,4-oxadiazole) derivatives. 5,5'-Bis(fluorodinitromethyl)-3,3'-bi(1,2,4-oxadiazole) was synthesised by fluorination of diammonium 5,5'-bis(dinitromethanide)-3,3'-bi(1,2,4-oxadiazole). For our previously reported analogue 5,5'-bis(trinitromethyl)-3,3'-bi(1,2,4-oxadiazole), a new synthetic route starting from new 3,3'-bi(1,2,4-oxadiazolyl)-5,5'-diacetic acid was developed. In this course also hitherto unknown 5,5'-dimethyl-3,3'-bi(1,2,4-oxadiazole) was isolated. The compounds were characterised by multinuclear NMR spectroscopy, IR and Raman spectroscopy, elemental analysis as well as mass spectrometry. X-ray diffraction studies were performed and the crystal structures for the 5,5'-dimethyl and 5,5'-(fluorodinitromethyl) derivatives are reported. The energetic 5,5'-(fluorodinitromethyl) and 5,5'-(trinitromethyl) compounds do not contain any hydrogen atoms and show remarkable high densities. Furthermore, the thermal stabilities and sensitivities were determined by differential scanning calorimetry (DSC) and standardised impact and friction tests. The heats of formation were calculated by the atomisation method based on CBS-4M enthalpies. With these values and the room-temperature X-ray densities, several detonation and propulsion parameters, such as the detonation velocity and pressure as well as the specific impulse of mixtures with aluminium, were computed using the EXPLO5 code.

Syntheses and Promising Properties of Dense Energetic 5,5′‐Dinitramino‐3,3′‐azo‐1,2,4‐oxadiazole and Its Salts

“…The presence of solvated methanol gives rise to the low calculated density.T he bond lengths of the oxadiazole ring are in accordance with those of other oxadiazoles. [9,11] Theb ond length N(5)-N(5A) is 1.258 , slightly shorter than that in 3 at 1.261 . [10] Thee ntire molecule is essentially planar as shown by the torsion angles of C (2) Compound 6 crystallizes as ad ihydrate in the triclinic space group P1 with ad ensity of 1.750 gcm À3 at 296 K. Theoxadiazole rings have bond lengths and angles comparable to 4.T he azo double bond is 1.248 , slightly shorter than that in the parent compound 4.The anion has ap lanar structure,a nd considerable hydrogen-bonding interactions between the cation and anion are seen (Figure 2b).…”

Theoretical investigations on 4,4′,5,5′‐tetranitro‐2,2′‐1H,1′H‐2,2′‐biimidazole derivatives as potential nitrogen‐rich high energy materials

“…Among the substituted energetic groups, nitro group (―NO 2 ) is still widely used for designing and synthesized novel energetic materials. With the advancement of energetic materials, there are more energetic groups which can be selected, such as amino (―NH 2 ), nitramine (―NHNO 2 ), trinitromethyl (―C(NO 3 ) 3 ) and fluorodinitromethyl (―CF(NO 3 ) 2 ) …”

Synthesis, Characterisation and Crystal Structures of Two Bi‐oxadiazole Derivatives Featuring the Trifluoromethyl Group

“…Herein we summarise the synthetic pathways for 3,3′‐bi‐(5‐trifluoromethyl‐1,2,4‐oxadiazole) (TFM 2 ‐ 1,2,4 BOD, 1 ) and the analogous 5,5′‐bi‐(2‐trifluoromethyl‐1,3,4‐oxadiazole) (TFM 2 ‐ 1,3,4 BOD, 2 ) and compare the density and thermal behaviour of the two compounds. The trifluoromethyl group serves as a non‐energetic moiety, in which fluorine atoms can be substituted stepwise by nitro groups, as reported previously for several 3,3′‐bi‐(5‐polynitromethyl‐1,2,4‐oxadiazole) derivatives 6b,c. 7…”

“…The bi‐1,2,4‐oxadiazole derivatives featuring the trinitromethyl and fluorodinitromethyl moieties have been reported previously and revealed good detonation and combustion properties, whereas the trinitromethyl compound shows a relatively low thermal stability, decomposing at 124 °C 6c. 7 For the bi‐1,3,4‐oxadiazole derivatives that are assumed to be thermally more stable, the heats of formation for compounds containing the difluoronitromethyl ( 3 ), fluorodinitromethyl ( 4 ), and trinitromethyl ( 5 ) groups attached were computed by ab initio calculations using the GAUSSIAN 09 program package15 at the CBS‐4M level of theory (Figure 2).…”

“…The effect of CF bonds on the heat of formation can clearly be observed in this series of polyfluoro/polynitro compounds. Using these values and an estimated density of 1.90 g cm −3 (minimumestimation supported by previous work)6c, 7 the detonation and combustion parameters were calculated using the EXPLO5 (V6.02) computer code (Table 3)17 and the ICT‐Thermodynamic Code (see the Supporting Information) 20. Providing the thermal stability of the non‐fused heterocyclic system is not decreased too much by the trinitromethyl moiety, compound 5 would be a suitable candidate as oxidiser in solid rocket propellants 18…”