Structure of 2',6'-dihydroxy-4,4'-dimethoxychalcone.

1-(2,6-Dihydroxy-4-methoxyphenyl)-3-(4-methoxyphenyl)-2-propen-1-o ne, C17H16O5, Mr = 300.31, orthorhombic, Pbca, a = 27.903 (3), b = 13.958 (2), c = 7.662 (1) A, V = 2984 (1) A3, Z = 8, D chi = 1.337 Mg m-3, lambda(Cu K alpha) = 1.5418 A, mu = 0.729 mm-1, F(000) = 1264, T = 295 K, R = 0.040 for 1702 observed reflections. Two intramolecular hydrogen bonds are observed. The hydroxyl H atom at O(6A) is hydrogen bonded to the C(9) carbonyl group with short distances O(6A)...O(9) = 2.406 (3) and O(9)...H(6A) = 1.38 (3), O(6A)--H(6A) = 1.09 (3) A, the angle O(6A)--H(6A)...O(9) is 153 (4) degrees. The other hydrogen bond is of the C--H...O type with distances C(8)...O(2A) = 2.778 (4), H(8)...O(2A) = 2.09 (3) A and the angle around H(8) is 124 (2) degrees. Conjugation is observed between the aromatic rings and the central enone system. The molecule is not planar, the angle between the planes of the phenyl rings being 13.1 (4) degrees. Intermolecular O--H...O bonds with distances O(6A)...O(2A) = 2.689 (2), H(2A)...O(6A) = 1.86 (4) A and angle O(2A)--H...O(6A) = 176 (4) degrees form endless chains of molecules along b.