Acta Cryst. (2007). E63, o3894 [ doi:10.1107/S1600536807040834 ]
Abstract: A second polymorph of coumarin-3-carboxylic acid (2-oxo-2H-1-benzopyran-3-carboxylic acid), C10H6O4, is reported in the P21/c space group. The structure shows intermolecular hydrogen bonding between the carboxyl groups on pairs of molecules related by an inversion centre, as well as a number of C-HO contacts.
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