PSEUDOSYMMETRY IN 2,5-DIMETHYL-1,4-BENZENEDIOL

The title compound, C8H10O2, was prepared from diacetyl by a high temp erature and pressure reaction. Pseudosymmetry in the structure results in diffraction symmetry enhancement for half the reflections and the possibility of twinning and stacking faults. The structure consists of two independent but pseudosymmetrically-related P2(1)/c substructures , each having centrosymmetric molecules on centres of inversion which are strongly hydrogen bonded to symmetry-related molecules to form lay ers perpendicular to c. The structure may be described as an occupanc y modulation, ordering a disordered parent structure in Pnma symmetry to form, upon change of axes, the P2(1)/c structure reported. The hydr oxyl H atoms have two site options corresponding to alternative hydrog en-bonding patterns and the methyl H atoms in one substructure are rot ationally disordered.