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.
Highlights
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
E65, o327– o328], the molecular components do not form conventional dimeric units, as an antiplanar conformation adopted by the OH group favors the association of molecules in chains stabilized by linear O—HÁ Á ÁO hydrogen bonds
Two polymorphs are known for 2,6-dimethoxybenzoic acid
Summary
Two polymorphs are known for 2,6-dimethoxybenzoic acid. Polymorph (I ) crystallizes in the orthorhombic space group P212121 with one molecule in the asymmetric unit (Swaminathan et al, 1976; Bryan & White, 1982; Portalone, 2009). As a result of the antiplanar conformation adopted by the OH group, the molecular components are associated in the crystal in chains stabilized by linear O—HÁ Á ÁO hydrogen bonds. Polymorph (I ) crystallizes in the tetragonal space group P41212 with one molecule in the asymmetric unit (Portalone, 2011). In the crystal of the second polymorph, the synplanar conformation of the OH group favours the formation of dimers through O—HÁ Á ÁO hydrogen bonds. In this article, it is reported the crystal structure of a third polymorph, (I ), of 2,6-dimethoxybenzoic acid produced unexpectedly during an attempt to synthesize co-crystals of 5-fluorouracil with the title compound. The pattern of bond lengths and bond angles of the phenyl ring is consistent with that reported in the structure determination of the two previously determined polymorphs, and a comparison of the present results with those obtained for similar benzene derivatives (Colapietro et al, 1984; Irrera et al, 2012; Portalone, 2012) shows no appreciable effects of the crystal environment on the ring deformation induced by substituents
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
