Refinement of the crystal structure of <i>p</i>-benzoquinone at –160°C

Abstract

C6H402, monoclinic, P2~/a, a = 6.763 (3), b --- 6.735 (3), c = 5.711 (3) A, fl = 99.55 (15) ° at -160°C, Z = 2, D e (-160°C) = 1.4 g cm -3, 2(Mo K~t~) = 0.70926, 2(Mo Kct2) =- 0.71354 A, p(Mo Ka) = 1.2 cm -~. The best plane of the molecule makes an angle of 3.2 ° with the plane (201). In contrast to earlier room-temperature X-ray studies it has been found that at -160°C the molecules are not strictly planar, but have a slight chair form with C2h (2/m) symmetry.