4-Butyl­amino-3-nitro­benzoic acid

The asymmetric unit of the title compound, C(11)H(14)N(2)O(4), comprises four crystallographically independent mol­ecules (A, B, C and D) with similar geometries. In each mol­ecule, the butyl­amino side chain is in an extended conformation, and the carboxyl and butyl­amino groups are almost coplanar with the attached benzene ring; the nitro group is slightly twisted away from the benzene ring. In the asymmetric unit, the benzene rings of mol­ecules A, B and C are stacked parallel to one another, with a centroid–centroid distance of 3.6197 (11) or 3.6569 (11) Å, indicating π–π inter­actions. An intra­molecular N—H⋯O hydrogen bond is observed in each independent mol­ecule. In addition to the π–π inter­actions, the crystal packing is consolidated by inter­molecular O—H⋯O and C—H⋯O hydrogen bonds and C—H⋯π inter­actions. The crystal studied was a non-merohedral twin. The minor twin component refined to a value of 0.290 (1).