Crystal Structure of Benzene at −3° C.

Abstract

A PRELIMINARY determination¹ of the crystal structure of benzene at −22° C. showed that the crystals are orthorhombic. space-group Pbca, with four centro-symmetrical molecules in the unit cell, and that the normals to the planes of the molecules are roughly perpendicular to the b-axis and inclined at about 50° to the c-axis. We have now completed the first stage of refinement of the structure at −3° C. Crystals were grown in Lindemann glass tubes of wall thickness 0.05 mm. and bore 0.36 mm. by the method of Keesom and Taconis² as modified by later workers³. 288 independent reflexion intensities representing 56 per cent of the total possible with copper radiation were estimated visually from oscillation photographs about all three principal axes. Chromium-K radiation was used to obtain accurate values of the unit cell dimensions by the Straumanis method; the revised dimensions are a = 7.46₀, b = 9.66₆ and c = 7.03₄ A.