Dobson A J, Gerkin R E
Department of Chemistry, Ohio State University, Columbus 43210, USA.
Acta Crystallogr C. 1998 Feb 15;54 ( Pt 2):253-6. doi: 10.1107/s0108270197013115.
3-Aminopyrazole-4-carboxylic acid, C4H5N3O2, crystallized in the non-centrosymmetric space group P21 in the zwitterionic form. Intermolecular N--H...O hydrogen bonds with N...O distances of 2.768 (2) and 2.747 (2) A link molecules into two sets of chains propagating along [110] 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) degrees. The dihedral angles between the core plane and the planes of the carboxylate group and the amino group are in the region of 2 and 37 degrees, respectively.
3-氨基吡唑-4-羧酸（C4H5N3O2）以两性离子形式结晶于非中心对称空间群P21中。分子间N-H...O氢键的N...O距离为2.768(2)和2.747(2) Å，将分子连接成两组沿[110]和[110]方向延伸的链。这两组链通过强氢键交联。由此形成了一个复杂的氢键网络。存在一个分子内氢键。吡唑核心近乎平面；构成两条链的分子的最佳拟合核心平面之间的二面角为82.2(1)度。核心平面与羧基平面和氨基平面之间的二面角分别在2度和37度左右。
