(plus or minus)-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
AbstractThe 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 OO = 2.673 (4) A and O-HO = 158Degrees having glide-related components, with centrosymmetrically related pairs of chains following axes perpendicular to b. Close intermolecular C-HO contacts exist for both the ketone and the carboxyl group. The energetics of the epimers and of their crystallization mode are discussed.