4-Amino-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide–2-nitrobenzoic acid (1/1)

In the asymmetric unit of the title co-crystal, C12H14N4O2S·C7H5NO4, the sulfamethazine and 2-nitrobenzoic acid molecules form a heterodimer through intermolecular amide–carboxylic acid N—H...O and carboxylic acid–pyrimidine O—H...N hydrogen-bond pairs, giving a cyclic motif [graph set R22(8)]. The dihedral angle between the two aromatic ring systems in the sulfamethazine molecule is 88.96 (18)° and the nitro group of the acid is 50% rotationally disordered. Secondary aniline N—H...Osulfone hydrogen-bonding associations give a two-dimensional structure lying parallel to the ab plane.