Dimorphic forms of 3,6‐dinitrodurene in a single space group

3,6‐Dinitrodurene (1,2,4,5‐tetramethyl‐3,6‐dinitrobenzene), C₁₀H₁₂N₂O₄, has been crystallized in two polymorphic forms which may be distinguished by their colours in the solid state. Polymorph I gives clear colourless prismatic crystals, while polymorph II crystallizes in the dark and under an inert atmosphere as irregular purple blocks. Both forms belong to the space group C2/c, with both asymmetric units containing two half‐molecules. One molecule is located on an inversion centre and the other lies on a twofold axis. The polymorphism arises from different orientations of the twofold axis: in form I, this axis passes through the mid‐points of two C—C bonds of the benzene ring and, as a consequence, all atoms in the asymmetric unit are in general positions. In form II, the N atoms of the nitro groups and the C_ipso atoms are located on the binary axis. Comparing phases I and II, slightly different conformations are observed for the nitro substituents, while the stacking structures are very similar.