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organic compounds
In contrast to the previously investigated hydrated form, anhydrous 2,4,6-trinitro-1,3,5-benzenetriol, C6H3N3O9, crystallizes in a non-centrosymmetric space group and shows non-linear optical activity in solution and in the solid state. The nitro groups are rotated out of the plane of the ring, the degree of twist being related to the number of intramolecular hydrogen bonds.