Crystal structures of 1-hydroxy-4-propyloxy-9,10-anthraquinone and its acetyl derivative

Abstract

1-Hydroxy-4-propyloxy-9,10-anthraquinone, C17H14O4, (I), and its acetyl derivative, 4-acetyloxy-4-propyloxy-9,10-anthraquinone, C19H16O5, (II), were synthesized from the commercially available dye quinizarin. In both compounds, the anthraquinone frameworks are close to planarity. There is a large difference in the conformation of the propyloxy group; the molecule of (I) adopts a gauche conformation [O—C—C—C = −64.4 (2)°], although the molecule of (II) takes a trans-planar conformation (zigzag) [O—C—C—C = 176.1 (3)°]. In the molecule of (I), there is an intramolecular O—H...O hydrogen bond. In both crystals, the molecules are linked by C—H ...O hydrogen bonds. A difference in the molecular arrangements of (I) and (II) is found along the stacking directions.

Keywords

• crystal structure
• anthraquinone
• hydrogen bonding
• π–π stacking
• C—H ...O interactions