Crystal Structure of 44′-Dihydroxydiphenyl

Abstract

CRYSTALS of 44′-dihydroxydiphenyl can be obtained as thin plates from alcohol–water solution or by sublimation. By optical and X-ray examination, they are found to be monoclinic with the b- and c-axes in the plane of the plate. The unit cell constants are: a = 10.54 ± 0.05 A., b = 5.36 ± 0.02 A., c = 7.95 ± 0.05 A., β = 95° 30′ ± 1°. The space group is P2₁/c, and since there are only two molecules in the unit cell (calculated from a density of 1.380 gm./c.c.) they must lie in special positions such that molecular centres of symmetry coincide with the centres of symmetry in the cell. Although there are other ways in which this condition might be satisfied, such as by free rotation about the central C—C bond, or rotation of the molecule as a whole in the crystal, the obvious inference is that the molecule is centro-symmetric by having its two aromatic rings coplanar.