Crystal structure of 2,5-dihydroxyterephthalic acid from powder diffraction data

Abstract

The crystal structure of anhydrous 2,5-dhydroxyterephthalic acid, C8H6O6, was solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The published structure of 2,5-dihydroxyterephthalic acid dihydrate was also optimized. The carboxylic acid groups form strong hydrogen bonds, which form centrosymmetric rings with graph set R 2 2(8). These hydrogen bonds link the molecules into chains along [011]. There is an intramolecular O—H...O hydrogen bond between the hydroxyl group and the carbonyl group of the carboxylic acid. The hydrogen bonding in the dihydrate is very different. Although the intramolecular hydroxy/carboxylic acid hydrogen bond is present, the water molecule acts as an acceptor to the carboxylic acid and a donor to two other oxygen atoms. The carboxylic acid groups do not interact with each other directly.