STRUCTURE OF 1,3-CYCLOPENTANEDIONE

1,3-Cyclopentanedione, C5H6O2, Mr -= 98·10, monoclinic, C2/c, a = 7·451 (2), b = 12.853 (3), c = 10.754 (2) Å, β = 111-90 (2) °, V= 956.2 (3) Å 3, Z = 8, Dx = 1.37 g cm-3, m.p. 422-425 K, λ(Mo Kaα) = 0·71069 Å, μ = 0.65 cm-l, F(000) = 416, T = 292 K, final R = 0·083 for 486 observed reflections. The molecules adopt the enol form and are connected head-to-tail by hydrogen bonds in which the O(1)· O(2′) distance is 2·542 (8)Å. The molecules lie in chains approximately in one plane parallel to b and inclined by about 12 ° to the crystallographic plane (100); the molecules themselves are planar, within error limits. Strong elongation of the vibrational ellipsoids of non-H atoms perpendicular to the plane of the molecules is observed. A pressuregenerated phase transition was observed in the crystals of 1,3-cyclopentanedione below 0.3 GPa. © 1990 International Union of Crystallography.