Crystal structure and Hirshfeld surface analysis of a third polymorph of 2,6-di-meth-oxy-benzoic acid.

ABSTRACT: A third crystalline form of the title compound, C₉H₁₀O₄, crystallizing in the centrosymmetric monoclinic space group P2₁/c, has been identified during screening for co-crystals. The asymmetric unit comprises a non-planar independent mol-ecule with a synplanar conformation of the OH group. The sterically bulky o-meth-oxy substituents force the carb-oxy group to be twisted away from the plane of the benzene ring by 74.10?(6)°. The carb-oxy group exhibits the acidic H atom disordered over two sites between two O atoms. A similar situation has been found for the second tetra-gonal polymorph reported [Portalone (2011 ?). Acta Cryst. E67, o3394-o3395], in which mol-ecules with the OH group in a synplanar conformation form dimeric units via strong O-H?O hydrogen bonds. In contrast, in the first ortho-rhom-bic form reported [Swaminathan et al. (1976 ?). Acta Cryst. B32, 1897-1900; Bryan & White (1982 ?). Acta Cryst. B38, 1014-1016; Portalone (2009 ?). Acta Cryst. E65, o327-o328], the mol-ecular components do not form conventional dimeric units, as an anti-planar conformation adopted by the OH group favors the association of mol-ecules in chains stabilized by linear O-H?O hydrogen bonds.

SUBMITTER: Portalone G 

PROVIDER: S-EPMC7784654 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature