Hydrogen bonding in 4-aminohippuric acid.

The title acid, C9H10N2O3, crystallized in the non-centrosymmetric space group P2(1)2(1)2(1) with one molecule in the asymmetric unit. Four hydrogen bonds occur whose donor-acceptor distances are: O1...O3 2.630 (2), N1...O3 3.090 (2), N2...O1 3.099 (2), and N2...O2 3.022 (2) A, and whose angles fall in the range 163 (2)-173 (2) degrees. The H atoms in these bonds are ordered. Cyclic hydrogen-bonded dimers are not formed; through second-level graphs, only hydrogen-bonded chains occur. These form a strongly three-dimensional array of hydrogen bonds. The dihedral angle between the core plane and the carboxyl plane is 54.8 (2) degrees, and between the core plane and the plane of the amino group, 34 (1) degree. The structure is compared with a previous determination by Chakrabarti & Dattagupta [Z. Kristallogr. (1993), 207, 53-58] and with the structure of the parent molecule, hippuric acid.