8,16-methano-16H-dinaphtho[2,1-d:1',2'-g]-[1,3]dioxocine-2,14-diol

The symmetry of the chemical structure of the title compound, C23H16O4, is not preserved in the crystal structure; two conformational isomers are present as naphthalene components are splayed away from each other and twisted in order to separate the aromatic H atoms H14 and H26. The chevron-shaped molecules are stacked on top of one another. Four such stacks (two antiparallel pairs) are apparent when the unit cell required by the centrosymmetry of the space group. The is viewed along the z axis. Both the conformation of the molecule and the orientation of the oxocine (O1 and O7) and phenolic (O18 and O27) O atoms, as defined by the vector from C4 to C6 (the methane bridgehead atoms), are reversed between adjacent molecules within each stack. This orientation reversal stacks the oxocine O atoms and the phenolic O atoms from neighboring molecules roughly on top of each other and places all O atoms, along with all hydrogen bonds, near the planes y = +/- n/2. The two intermolecular hydrogen bonds per molecule involve only the phenolic O atoms. Energy minimization of the crystal structure with MOPAC [Stewart (1983). QCPE No. 455. Indiana Univ., USA] yields much the same structure. The proximity of H atoms H14 and H26 to each other and the phenolic rings of the opposite naphthalene components, even with the distortion, is sufficient to explain the downfield shift of 1.1 p.p.m. observed for these protons in NMR spectrum.