The Crystalline Structure of Benzene

Abstract

BY means of X-ray measurements upon single crystals, using the rotation method, I have been able to determine the unit cell of benzene. The cell is simple orthorhombic, of dimensions a=7.44 A., b=9.65 A., and c=6.81 A. at -22° C., and contains four molecules. As a result of the examination of about one hundred crystal planes, the space group was found to be Q¹⁵_h (orthorhombic bipyramidal). From this it can be shown that in the crystal the molecule has a centre but no planes of symmetry. Taking a standard molecule at a corner of the cell, the three derived molecules are situated at the centres of the cell faces. This pseudo-face-centred arrangement accounts both for the fact that the plane (111) gives the strongest X-ray reflections, and also for the bipyramidal habit of benzene crystals.