COMPLEX NETWORK OF HYDROGEN-BONDS IN 3-AMINOPYRAZOLE-4-CARBOXYLIC ACID

3-Aminopyrazole-4-carboxylic acid, C4H5N3O2, crystallized in the non-c entrosymmetric space group P2(1) in the zwitterionic form. Intermolecu lar N-H ... O hydrogen bonds with N ... O distances of 2.768 (2) and 2 .747 (2) Angstrom link molecules into two sets of chains propagating a long [1 (1) over bar 0] and [110]. The two sets of chains are crosslin ked by strong hydrogen bonds. A complex network of hydrogen bonds ensu es. 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)degrees. The dihe dral angles between the core plane and the planes of the carboxylate g roup and the amino group are in the region of 2 and 37 degrees, respec tively.