(±)-2-Oxocyclohexanepropionic acid: dual conformational selection and hydrogen bonding in a δ-keto acid, and a two-phase technique for crystallizing acids by contact with aqueous solutions of their salts

• Published in: Acta crystallographica. Section C, Crystal structure communications Crystal structure communications, 2003-11, Vol.59 (11), p.o638-o640
• Main Authors: Lalancette, Roger A., Thompson, Hugh W.
• Format: Article
• Language: English
• Subjects: Aliphatic, non-condensed and condensed benzenic, and alicyclic compounds; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Organic compounds; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0108-2701; 1600-5759
• DOI: 10.1107/S0108270103020638

The asymmetric unit of the title compound, C9H14O3, consists of two mol­ecules having conformations that differ by 121.7 (4)° 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), the dimers are asymmetric, formed by pairing mol­ecules of identical chirality but differing conformational type [O⋯O = 2.681 (2) and 2.654 (2) Å, and O—H⋯O = 175 (3) and 176 (3)°]. 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.