(2S*,4aR*,8aS*)-6-Oxoperhydronaphthalene-2-carboxylic acid: dual hydrogen-bonding modes in a bicyclic ζ-keto acid

The title racemate, C11H16O3, displays two different hydrogen-bonding modes in the crystal structure. The chosen asymmetric unit consists of two mol­ecules of identical handedness that differ in the rotation of their carboxyl groups and are linked by an acid-to-ketone hydrogen bond [O⋯O = 2.7219 (17) A and O—H⋯O = 174°]. The remaining carboxyl forms a centrosymmetric dimer with a second such unit [O⋯O = 2.6368 (15) A and O—H⋯O = 174°], while the ketones at the extremities of this four-mol­ecule aggregate remain unengaged. Five inter­molecular C—H⋯O close contacts were found.