(+/-)-2-oxocyclohexanepropionic acid: dual conformational selection and hydrogen bonding in a delta-keto acid, and a two-phase technique for crystallizing acids by contact with aqueous solutions of their salts.
The asymmetric unit of the title compound, C(9)H(14)O(3), consists of two molecules having conformations that differ by 121.7 (4) degrees in their rotation about the equatorial substituent bond, so that the side chain extends away from the ring in different directions in the two species. The hydrogen-bonding mode is acid-to-acid dimerization. However, despite the centrosymmetric space group (P-1), the dimers are asymmetric, formed by pairing molecules of identical chirality but differing conformational type [O...O = 2.681 (2) and 2.654 (2) A, and O-H...O = 175 (3) and 176 (3) degrees ]. Two intermolecular C-H...O=C close contacts exist, involving the ketone group of one of the molecules. A two-phase technique is described for slow reforming of crystals of a water-insoluble acid by contact with an aqueous solution of its water-soluble salt.
Lalancette
Roger A
RA
Department of Chemistry, Rutgers University, Newark, NJ 07102, USA. rogerlal@andremeda.rutgers.edu
Thompson
Hugh W
HW