title: Little change but great effect: varying supramolecular interactions in 2,5-dimethoxyterephthalic acid and 2,5-diethoxyterephthalic acid.
abstract: The title terephthalic acid derivatives, namely 2,5-dimethoxyterephthalic acid, C(10)H(10)O(6), (I), and 2,5-diethoxyterephthalic acid, C(12)H(14)O(6), (II), exhibit nearly planar molecular structures, with maximum deviations from the least-squares planes calculated for all non-H atoms of 0.0418 (6) and 0.0902 (10) Å for (I) and (II), respectively. The molecules of both title compounds contain an inversion centre and thus the asymmetric unit of both crystal structures consists of only half a molecule. It is a remarkable fact that a comparatively small change in the substitution of the terephthalic acid [dimethoxy in (I) versus diethoxy in (II)] causes major differences in the dominating supramolecular interactions. While in (II) the packing structure is stabilized by typical intermolecular hydrogen-bonded carboxylic acid dimer interactions, the carboxyl group in (I) forms an unusual intramolecular hydrogen bond with the O atom of the neighbouring methoxy group.
authors: Institut für Physikalische Chemie, TU Bergakademie Freiberg, Leipziger Strasse 29, D-09596 Freiberg/Sachsen, Germany.
authors: Tony
authors: T
authors: Böhle
authors: Frank
authors: F
authors: Eissmann
authors: Wilhelm
authors: W
authors: Seichter
authors: Edwin
authors: E
authors: Weber
authors: Florian O R L
authors: FO
authors: Mertens