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organic compounds
3-Aminopyrazole-4-carboxylic acid, C4H5N3O2, crystallized in the non-centrosymmetric space group P21 in the zwitterionic form. Intermolecular N-HO hydrogen bonds with NO distances of 2.768 (2) and 2.747 (2) Å link molecules into two sets of chains propagating along [10] and [110]. The two sets of chains are crosslinked by strong hydrogen bonds. A complex network of hydrogen bonds ensues. There is a single intramolecular hydrogen bond. The pyrazole core is closely planar; the dihedral angle between the best-fit core planes of the molecules making up the two chains is 82.2 (1)°. The dihedral angles between the core plane and the planes of the carboxylate group and the amino group are 2 and 37 °, respectively.