N-(2,4,6-Trichlorophenyl)maleamic acid

In the crystal structure of the title compound, C10H6Cl3NO3, the conformation of the amide bond is trans. The C = O and O-H bonds of the acid group are in the relatively rare anti position to each other. This is a consequence of the intramolecular O-H center dot center dot center dot O hydrogen bond donated to the amide carbonyl group stabilizing the molecular structure. In the crystal, intermolecular N-H center dot center dot center dot O hydrogen bonds link the molecules into zigzag chains along the c axis.