Hydrogen-Bonding Pattern of an α,β-Unsaturated δ-Keto Acid: 1',3'-Dihydro-2-methyl-6-oxospiro[2-cyclohexene-1,2'-2'H-indene]-3-carboxylic Acid

The title compound, C₁₆H₁₆O₃, adopts a chiral conformation incorporating a flattened cyclohexene ring, with pairs of molecules forming centrosymmetric carboxyl dimers. The acid group is rotated 18 (1)° from coplanarity with the alkene and displays typical carboxyl disorder; the methyl group is rotationally disordered.

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