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- Title
Conformational dimorphism in o-nitrobenzoic acid: alternative ways to avoid the O. . .O clash.
- Authors
Aziz Ibragimov; Jamshid Ashurov; Ibragimov, Bakhtiyar; Ai Wang; Halima Mouhib; Englert, Ulli
- Abstract
Polymorphism is a challenging phenomenon and the competitive packing alternatives which are characteristic for polymorphs may be encountered for essentially rigid molecules. A second crystal form of the well known compound o-nitrobenzoic acid, C7H5NO4, an important intermediate in the production of dyes, pharmaceuticals and agrochemicals, is described. Although obtained serendipitously, its intra- and intermolecular features match expectations from database searches and theoretical calculations. O-H…O hydrogen-bonded carboxylic acid dimers represent the building blocks in both polymorphs. For steric reasons and in agreement with a calculated potential energy surface, the carboxylic acid and nitro groups cannot simultaneously be coplanar with the benzene ring but have to tilt. In the well established crystal form, this out-ofplane torsion is more pronounced for the nitro substituent. In contrast, the new polymorph is characterized by a major tilt of the carboxylic acid group. The molecules in both alternative crystal forms achieve a similar compromise with respect to acceptable intramolecular O. . .O contacts.
- Subjects
DIMORPHISM (Crystallography); NITROBENZOIC acid; CARBOXYLIC acids; CHEMICAL synthesis
- Publication
Acta Crystallographica Section C: Structural Chemistry, 2016, Vol 72, Issue 7, p566
- ISSN
2053-2296
- Publication type
Article
- DOI
10.1107/S2053229616009591