4-(sec-Butyl-amino)-3-nitro-benzoic acid.

The asymmetric unit of title compound, C(11)H(14)N(2)O(4), consists of two crystallographically independent mol-ecules (A and B). In each, intra-molecular N-H⋯O hydrogen bonds generate S(6) ring motifs. The mean plane of the nitro group forms dihedral angles of 4.5 (3) and 0.5 (3)° with the benzene ring in mol-ecules A and B, respectively. In mol-ecule A, there is disorder of the butyl-amino group which corresponds to an approximate 180° rotation about the N-C(H) bond, forming two sites with refined occupancies of 0.722 (6) and 0.278 (6). Mol-ecule B is similarly disordered but in addition there is further rotational disorder about the C(H)-C(H(2)) bond giving a ratio of occupancies for three components of 0.42:0.35:0.23. In the crystal structure, inter-molecular O-H⋯O hydrogen bonds link mol-ecules into centrosymmetric dimers generating R(2) (2)(8) ring motifs. The crystal structure is also stabilized by weak inter-molecular C-H⋯O inter-actions.