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organic compounds
The crystal structures of 2,2'-biimidazole-1,1'-diacetone, C12H14N4O2, and 2,2'-biimidazole-1,1'-diacetonitrile, C10H8N6, have been determined. Both molecules crystallize with coplanar rings having substituents in a trans disposition with a center of inversion located midway between the C atoms.