4-(But-3-enylamino)-3-nitrobenzoic acid

The asymmetric unit of the title compound, C(11)H(12)N(2)O(4), contains 12 crystallographically independent molecules, labelled A to L. The nitro and carboxyl groups are twisted slightly out of the plane of the attached benzene ring in all independent molecules except molecules G and D. The nitro group is coplanar with the benzene ring in molecule G and the carboxyl group is coplanar with the benzene ring in molecule D. The orientation of the butyl group with respect to the rest of the molecule is different in some of the independent molecules, with the C-C-C-C torsion angles varying from 104.2 (5) to 126.6 (7)degrees. In each independent molecule, an intramolecular N-H center dot center dot center dot O hydrogen bond generates an S(6) ring motif. In the crystal structure, the 12 independent molecules exist as six pairs of O-H center dot center dot center dot O hydrogen-bonded R(2)(2)(8) dimers. In addition, C-H center dot center dot center dot O hydrogen bonds are observed.