5-Oxocyclooctanecarboxylic acid: hydrogen-bonding pattern and conformational disorder in a medium-ring epsilon-keto acid

Molecules of the title compound, C9H14O3, adopt a chiral 'boat-chair' confo rmation, in which the carboxyl group avoids potential cross-ring ketone int eractions by an outward 'equatorial' orientation. The asymmetric unit conta ins two such molecules, one conformationally fixed without disorder, (I), a nd the other, (I'), extensively disordered, both in the bond lengths and an gles of the carboxyl and by a coupled 'up-down' conformational disordering [ratio of 60:40 (1)] of the remote ends of the boat-chair system. Each mole cule in the asymmetric unit forms a centrosymmetric hydrogen-bonded carboxy l dimer with a second molecule of its own type. For (I), O . . . O = 2.658 (3) Angstrom and O-H . . . O = 174 degrees. For (I'), O . . . O = 2.653 (3) Angstrom and O-H . . . O = 165 degrees. A number of intermolecular C=O . . . H-C close contacts are found.