(+/-)-cis-2-Methyl-4-oxocyclohexanecarboxylic acid: catemeric hydrogen bonding in a delta-keto acid derived from Hagemann's ester.

The title compound, C(8)H(12)O(3), crystallizes as acid-to-ketone hydrogen-bonding catemers, in which hydrogen bonds progress from the carboxyl group of each molecule to the ketone group of a translationally related neighbor [O.O = 2.738 (3) A and O-H.O = 153 (4) degrees ]. Four separate hydrogen-bonding chains proceed through the cell in centrosymmetrically related pairs along axes lying in the ab plane. Three intermolecular C-H.O close contacts exist involving both carboxyl O atoms. Factors contributing to the choice of hydrogen-bonding mode are discussed.