Hydrogen bonding in 4-aminohippuric acid

The title acid, C₉H₁₀N₂O₃, crystallized in the non-centrosymmetric space group P2₁2₁2₁ 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) Å, and whose angles fall in the range 163 (2)-173 (2)°. 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)°, and between the core plane and the plane of the amino group, 34 (1)°. 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.