The epimeric 9-oxobicyclo[3.3.1]nonane-3-carboxylic acids: hydrogen-bonding patterns of the endo acid and the lactol of the exo acid.
The two delta-keto carboxylic acids of the title, both C(10)H(14)O(3), are epimeric at the site of carboxyl attachment. The endo (3alpha) epimer, (I), has its keto-acid ring in a boat conformation, with the tilt of the carboxyl group creating conformational chirality. The molecules form hydrogen bonds by centrosymmetric pairing of carboxyl groups across the corners of the chosen cell [O...O = 2.671 (2) A and O-H...O = 179 (2) degrees ]. Two close intermolecular C-H...O contacts exist for the ketone. The exo (3beta) epimer exists in the closed ring-chain tautomeric form as the lactol, 8-hydroxy-9-oxatricyclo[5.3.1.0(3,8)]undecan-10-one, (II). The molecules have conformational chirality, and the hydrogen-bonding scheme involves intermolecular hydroxyl-to-carbonyl chains of molecules screw-related in b [O...O = 2.741 (2) A and O-H...O = 177 (2) degrees ].
Papadakis
Markos M
MM
Carl A. Olson Memorial Laboratories, Department of Chemistry, Rutgers University, Newark, NJ 07102, USA.
Pavon
Jorge A
JA
Lalancette
Roger A
RA
Thompson
Hugh W
HW
D001643:Bridged Bicyclo Compounds / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular
D001643:Bridged Bicyclo Compounds; D002264:Carboxylic Acids