Pushing the Limits of Oxygen Balance in 1,3,4-Oxadiazoles

Gem-trinitromethyl groups were introduced into
a 1,3,4-oxadiazole ring to give the first example of a bifunctionalized
single five-membered ring with six nitro groups. 2,5-Bis­(trinitromethyl)-1,3,4-oxadiazole
(12) has a high calculated crystal density of 2.007 g
cm–3 at 150 K (1.941 g cm–3 at
293 K) and a very high positive oxygen balance (39.12%), which makes
it a strong candidate as a high energy dense oxidizer. The dihydroxylammonium
and dihydrazinium salts of bis­(trinitromethyl)-1,3,4-oxadiazole (5 and 6) exhibit excellent calculated detonation
properties (5, vD = 9266
m s–1, P = 38.9 GPa; 6, vD = 8900 m s–1, P = 36.3 GPa) and acceptable impact sensitivities (5 20 J, 6 19 J), which are superior to those
of RDX (7.4 J) and HMX (7.4 J). Such attractive features support the
application potential of the gem-polynitromethyl
group in the design of advanced energetic materials. Surprisingly,
2,5-bis­(trinitromethyl)-1,3,4-oxadiazole (12) is more
thermally stable and less sensitive than its bis­(dinitromethyl) analogue, 8.