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organic compounds
2,2'-Methylenebis(3-hydroxy-5,5-dimethylcyclohex-2-en-1-one), C17H24O4, forms crystals which appear tetragonal, but are actually orthorhombic. They are twinned on (110). The asymmetric unit consists of two very similar molecules, each with exact crystallographic C2 symmetry. Each molecule forms two strong intramolecular hydrogen bonds connecting the two cyclohexenone rings.