Concomitant polymorphism and conformational isomerism in 4-acetylresorcinol.

Two polymorphs of the title compound [systematic name: 1-(2,4-dihydroxyphenyl)ethanone], C(8)H(8)O(3), were investigated. The known structure [designated (I-M); P2(1)/c, Z = 4; previously investigated at room temperature by Robert, Moore, Eichhorn & Rillema (2007). Acta Cryst. E63, o4252] was redetermined at low temperature, and a new form [(I-O); P2(1)2(1)2(1), Z = 12] was discovered in the same sample. In both forms, the molecules are planar (apart from the methyl H atoms) and they contain intramolecular O-H...O=C hydrogen bonds. In polymorph (I-M), molecules are linked into chains by a single intermolecular O-H...O hydrogen bond, and the chains are linked into sheets by two C-H...O hydrogen bonds. Three O-H...O hydrogen bonds link the molecules of polymorph (I-O) into chains and neighbouring chains are connected by one C-H...O interaction to form an offset layer structure. Two weak methyl C-H...O interactions link the layers.