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The crystal structure of the metastable β-phase of toluene is determined from single crystal X-ray diffraction data using a Monte-Carlo method coupled to a constrained leastsquares refinement. At 105 K β-toluene is orthorhombic (space group Pbcn ; a = 13.85 A, b = 11.42 A, c = 7.39 A ; Z = 8). Relations between the packing of the molecules in this modification and in the normal crystalline α-phase are discussed.

The crystal and molecular structures of syndiotactic 2,4,6,8-tetraphenylnonane have been determined by direct methods and refinement from X-ray diffraction data. The unit cell is quadratic (space group I 4 1 /g) with, at room temperature, g  13.740, c  27.20 A, V = 5135.7 A, Z = 8 and contains one molecule in the asymmetric unit; the final weighted residual factor is r = 0.065 for 1541 observed reflexions. It is found that the aliphatic chain exhibits a gauche-gauche conformation in the middle of the chain.