The crystal and molecular structure of ovalene a quantitative X-ray investigation

The crystal structure of ovalene (octabenzonaphthalene) has been determined in detail. The space group is P 2$_{1}$/a, and the unit cell contains two planar, centro-symmetric molecules inclined at about 43 degrees to (010), with a distance of 3$\cdot $45 angstrom between the molecular planes. The structure has been refined by double Fourier series methods. The twelve chemically distinct carbon-carbon bonds in the molecule vary in length from 1$\cdot $355 to 1$\cdot $438 angstrom (probable error after correction for finite series effects about $\pm $ 0$\cdot $015 angstrom). These variations in bond length can be predicted by various theoretical treatments, and good agreement between theory and experiment is obtained. The extreme shortness of the bonds in 'exposed' positions on the periphery of the molecule, and the longer bonds in the interior, are special features of the results.