Four 3-cyanodifurazanyl ethers: potential propellants

In earlier papers, we described the synthesis and structures of bis(3-nitrofurazan-4-yl) ether, C4N6O7, (I), bis[3-(nitro-N,N,O-azoxy)furazan-4-yl] ether, C4N10O9, (II), and bis[3-(5H-[1,2,3]triazolo[4,5-c]furazan-5-yl)furazan-4-yl] ether, C8N14O5, (III). Here we compare the structures of (I)-(III) with those of four 3-cyanodifurazanyl ethers, namely bis(3-cyanofurazan-4-yl) ether, C6N6O3, (IV), 3-cyanofurazanyl 3-nitrofurazanyl ether, C5N6O5, (V), 3,4-bis(3-cyanofurazan4-yloxy)furazan, C8N8O5, (VI), and bis[3-(3-cyanofurazan4-yloxy)furazan-4-yl]diazene, C10N12O6, (VII). It was found that the geometric parameters of the difurazanyl ether fragments are similar in these structures and therefore not influenced by substituent effects; however, the conformation of this fragment is different, viz. structures (I), (III), (V) and (VI) have approximate C-2 symmetry, and structures (II), (IV) and (VII) have CS symmetry. Dense crystal packing (1.626-1.898 Mg m(-3)) is characteristic for all these hydrogen-free compounds. A linear correlation is also determined between crystal density and 'molecular density' (M/V), where M is the mass of a molecule and V is the molecular volume.