4-Cyclo-butyl-amino-3-nitro-benzoic acid.

The asymmetric unit of the title compound, C(11)H(12)N(2)O(4), contains two crystallographically independent mol-ecules with similar geometries. Both mol-ecules contain an intra-molecular N-H⋯O hydrogen bond. The dihedral angles between the benzene ring and the mean plane of the cyclo-butane ring are 38.29 (7) and 57.04 (8)° in the two mol-ecules, and the nitro group is twisted slightly away from the plane of the benzene ring [dihedral angles = 9.15 (12) and 9.55 (12)° in the two mol-ecules]. In the crystal, the independent mol-ecules are linked into dimers by O-H⋯O hydrogen bonds between their carboxyl groups, and C-H⋯O and C-H⋯π inter-actions are formed between dimers.