G. Portalone
Nov 23, 2011
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Influential Citations
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Journal
Acta Crystallographica Section E: Structure Reports Online
Abstract
A new crystalline form of 2,6-dimethoxybenzoic acid, C9H10O4, crystallizing in a tetragonal unit cell has been identified during screening for co-crystals. The asymmetric unit comprises a non-planar independent molecule with a synplanar conformation of the carboxy group. The sterically bulky o-methoxy substituents force the carboxy group to be twisted away from the plane of the benzene ring by 65.72 (15)°. The carboxy group is disordered over two sites about the C—C bond [as indicated by the almost equal C—O distances of 1.254 (3) and 1.250 (3) Å], the occupancies of the disordered carboxym H atoms being 0.53 (5) and 0.47 (5). In the known orthorhombic form reported by Swaminathan et al. [Acta Cryst. (1976), B32, 1897–1900], due to the antiplanar conformation adopted by the OH group, the molecular components are associated in the crystal in chains stabilized by linear O—H⋯O hydrogen bonds. However, in the new tetragonal polymorph, molecules form dimeric units via pairs of O—H⋯O hydrogen bonds between the carboxy groups.