N-(4-Methoxyphenyl)maleamic acid

In the title compound, C11H11NO4, the asymmetric unit contains two unique molecules, 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 molecules. The molecular structures are stabilized by a short intramolecular O—H⋯O hydrogen bond within each maleamic acid unit. In the crystal, intermolecular N—H⋯O hydrogen bonds link the molecules into zigzag chains extending along [10]. Weak intermolecular C—H⋯O hydrogen bonds also exist.

In the title compound, C 11 H 11 NO 4 , the asymmetric unit contains two unique molecules, 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 molecules. The molecular structures are stabilized by a short intramolecular O-HÁ Á ÁO hydrogen bond within each maleamic acid unit. In the crystal, intermolecular N-HÁ Á ÁO hydrogen bonds link the molecules into zigzag chains extending along [110]. Weak intermolecular C-HÁ Á ÁO hydrogen bonds also exist.
MT and JK thank the Grant Agency of the Slovak Republic (VEGA 1/0817/08) and Structural Funds, Interreg IIIA, for financial support to purchase the diffractometer. KS thanks the University Grants Commission, Government of India, New Delhi, for the award of a research fellowship under its faculty improvement program. Leiserowitz, L. (1976). Acta Cryst. B32, 775-802. Oxford Diffraction (2009

Comment
As a part of studying the effect of the ring and side chain substitutions on the crystal structures of biologically significant amides (Gowda et al., 2009a,b,c;Prasad et al., 2002), in the present work, the crystal structure of N-(4methoxyphenyl)maleamic acid (I) has been determined (Fig. 1). The asymmetric unit of the structure contains two unique molecules. Both the molecules are almost planar with r.m.s deviations of 0.047Å and 0.059Å for the two molecules (Fig. 1).
The conformations of the N-H and the C=O bonds in the amide segment are anti to each other. In the side chain, the amide C=O bond is anti to the adjacent C-H bond, while the carboxyl C=O bond is syn to the adjacent C-H bond.
Weak intermolecular C-H···O hydrogen bonds also exist in the structure.
The various modes of interlinking carboxylic acids by hydrogen bonds is described elsewhere (Leiserowitz, 1976). The packing of molecules involving dimeric hydrogen bonded association of each carboxyl group with a centrosymmetrically related neighbor has also been observed (Jagannathan et al., 1994).