STRUCTURES OF 2 CRYSTALLINE MODIFICATIONS OF LAPACHOL

2-Hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthalenedione, C15H14O3, M(r) = 242.26. Triclinic (LAPA I), P1BAR, a = 5.960 (1), b = 9.569 (2), c = 10.679 (2) angstrom, alpha = 96.82 (2), beta = 98.32 (2), gamma = 90.32 (2)-degrees, V = 598.2 (3) angstrom3 at 105 K, Z = 2, D(x) = 1.345 Mg m-3, lambda(Mo Kalpha) = 0.71073 angstrom, mu = 0.087 mm-1, F(000) = 256, T = 105 K, final R = 0.028 for 1249 unique observed reflections. Monoclinic (LAPA II), P2(1)/c, a = 6.035 (1), b = 9.427 (2), c = 20.918 (5) angstrom, beta = 98.27 (2)-degrees, V = 1177.7 (5) angstrom3 at 105 K, Z = 4, D(x) = 1.366 Mg M-3, lambda(Mo Kalpha) = 0.71073 angstrom, mu = 0.088 mm-1, F(000) = 512, T = 105 K, final R = 0.027 for 739 unique observed reflections. In both crystalline modifications of lapachol the naphthoquinone ring system is approximately planar, and the planar unsaturated side chain is twisted about 90-degrees with respect to the ring system. The crystal packings of LAPA I and II show that the molecules, in both cases, form dimers through OH...O hydrogen bonds around centres of symmetry.