N-(4-Meth-oxy-phen-yl)maleamic acid.

In the title compound, C(11)H(11)NO(4), the asymmetric unit contains two unique mol-ecules, both of which are almost planar, with r.m.s. deviations of 0.047 and 0.059 Å. The dihedral angles between the benzene ring and the plane of maleamic acid unit are 3.43 (5) and 5.79 (3)° in the two mol-ecules. The mol-ecular structures are stabilized by a short intra-molecular O-H⋯O hydrogen bond within each maleamic acid unit. In the crystal, inter-molecular N-H⋯O hydrogen bonds link the mol-ecules into zigzag chains extending along [10]. Weak intermolecular C-H⋯O hydrogen bonds also exist.