(±)-7-Oxo-1,2,3,4,4a,5,6,7-octahydronaphthalene-1-acetic acid: catemeric hydrogen bonding and diastereomeric disorder in a bicyclic unsaturated -keto acid
The 68.5:31.5 mixture of diastereoisomers obtained in the synthesis of the title compound, C12H16O3, yielded sharply melting crystals containing the same ratio of epimers, in a disordered crystallographic arrangement. The disorder resides almost entirely in the carboxymethyl side chain, but places the two sets of carboxyl O atoms at nearly identical paired spatial positions. Neither component displays significant carboxyl disorder, and the molecules aggregate as hydrogen-bonded carboxyl-to-ketone catemers [O…O = 2.673 (4) Å and O—H…O = 158°] having glide-related components, with centrosymmetrically related pairs of chains following axes perpendicular to b. Close intermolecular C—H…O contacts exist for both the ketone and the carboxyl group. The energetics of the epimers and of their crystallization mode are discussed.
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Document Type: Research Article
Publication date: 2004-04-01