title: Two (+)-alpha,4-dimethyl-2-oxocyclohexaneacetic acids: hydrogen bonding in a terpenoid gamma-keto acid and in a diastereomeric lactol.
abstract: The (+)-(alphaS,1S,4R)-diastereomer of the title structure, C10H16O3, aggregates in the solid as non-symmetric dimers with disorder in both carboxyl groups [O...O = 2.710 (5) and 2.638 (5) A]. The two molecules constituting the asymmetric unit pair around a pseudo-twofold rotational axis and differ only slightly in their distances and angles, but one methyl group displays rotational disorder absent in the other molecule. Five intermolecular C-H...O close contacts exist, involving both ketone groups. The (+)-(alphaR,1R,4R)-diastereomer exists in the crystal in its closed-ring lactol form, (3R,3aR,6R,7aR)-2,3,3a,4,5,6,7,7a-octahydro-7a-hydroxy-3,6-dimethylbenzo[b]furan-2-one, C(10)H(16)O(3), and aggregates as hydrogen-bonded catemers that extend from the hydroxyl group of one molecule to the carbonyl group of a neighbor screw-related along b [O...O = 2.830 (3) A and O-H...O = 169 degrees]. One close intermolecular C-H...O contact exists involving the carbonyl group.
authors.affiliation: Carl A. Olson Memorial Laboratories, Department of Chemistry, Rutgers University, Newark, NJ 07102, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Davison
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Kikolski
authors.forename: David
authors.initials: D
authors.lastname: Mostafavi
authors.forename: Roger A
authors.initials: RA
authors.lastname: Lalancette
authors.forename: Hugh W
authors.initials: HW
authors.lastname: Thompson