N-(3,4-Dimethylphenyl)maleamic acid

The title compound, C12H13NO3, crystallizes with four independent molecules in the asymmetric unit. The N—H bond and the C=O bond in the amide segment are anti to each other. The C=C double bond is cis configured and an intramolecular O—H⋯O hydrogen bond is formed in each molecule. The mean planes through the aromatic ring and the amide group –NHCO– are inclined at angles of 17.4 (3), 20.8 (2), 16.2 (2) and 11.2 (3)° in the four molecules. In the crystal, intermolecular N—H⋯O hydrogen bonds link the molecules into ribbons along the b axis.