N-(3-Chlorophenyl)maleamic acid

In the title compound, C10H8ClNO3, the molecular conformation is stabilized by two intramolecular hydrogen bonds. The first is a short O—H⋯O hydrogen bond within the maleamic acid unit and the second is a C—H⋯O hydrogen bond which connects the amide group with the phenyl ring. The maleamic acid unit is essentially planar, with an r.m.s. deviation of 0.044 Å, and makes a dihedral angle of 15.2 (1)° with the phenyl ring. In the crystal, intermolecular N—H⋯O hydrogen bonds link the molecules into C(7) chains running [010].

In the title compound, C 10 H 8 ClNO 3 , the molecular conformation is stabilized by two intramolecular hydrogen bonds. The first is a short O-HÁ Á ÁO hydrogen bond within the maleamic acid unit and the second is a C-HÁ Á ÁO hydrogen bond which connects the amide group with the phenyl ring. The maleamic acid unit is essentially planar, with an r.m.s. deviation of 0.044 Å , and makes a dihedral angle of 15.2 (1) with the phenyl ring. In the crystal, intermolecular N-HÁ Á ÁO hydrogen bonds link the molecules into C(7) chains running [010].

Experimental
MT and JK thank the Grant Agency of the Slovak Republic (VEGA 1/0817/08) and the Structural Funds, Interreg IIIA, for financial support in purchasing 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.

Comment
As a part of studying the effect of ring and side chain substitutions on the crystal structures of biologically significant amides (Gowda et al., 2010a,b;Prasad et al., 2002;Shakuntala et al., 2009), the crystal structure of N-(3-chlorophenyl)maleamic acid (I) has been determined (Fig. 1).The conformations of the N-H and the C=O bonds in the amide segment are anti to each other. The conformation of the N-H bond is also anti to the meta-Cl group in the phenyl ring.In the maleamic acid moiety, 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. The observed rare anti conformation of the C=O and O-H bonds of the acid group is similar to that observed in N-(2-methylphenyl)-maleamic acid (Gowda et al., 2010b), N-(2,5-dichlorophenyl)-maleamic acid (Shakuntala et al., 2009) and N-(3,5-dichlorophenyl)-maleamic acid (Gowda et al., 2010a).
The molecular structure of (I) is stabilized by two intramolecular hydrogen bonds ( Figure 1): the first is a short O-H···O hydrogen bond within maleamic acid unit and the second is a C-H···O hydrogen bond which connects the amide group with the phenyl ring. Amidic O1 atom acts as bifurcated acceptor of O2-H2A···O1 and C6-H6···O1 intramolecular hydrogen bonds ( Table 1).The maleamic acid unit is essentially planar, with r.m.s.deviation of 0.044 Å and makes dihedral angle of 15.2 (1)° with the phenyl ring. The torsion angle C1-N1-C5-C6 = -17.6 (2)° defines the orientation of the phenyl ring towards the central amide group -NHCO. The molecular structure is stabilized by two types intramolecular C-H···O and O-H···O interactions with H···O distances of 1.60 and 2.31 Å respectively and one intermolecular N-H···O hydrogen bonds link the molecules into chains with graph-set notation C(7) (Bernstein et al., 1995) running along the [0 1 0] direction, Table 1, Figure 2.

Experimental
The solution of maleic anhydride (0.025 mol) in toluene (25 ml) was treated dropwise with the solution of 3-chloroaniline (0.025 mol) also in toluene (20 ml) with constant stirring. The resulting mixture was warmed with stirring for over 30 min and set aside for an additional 30 min at room temperature for completion of the reaction. The mixture was then treated with dilute hydrochloric acid to remove the unreacted 3-chloroaniline. The resultant solid N-(3-chlorophenyl)maleamic acid was filtered under suction and washed thoroughly with water to remove the unreacted maleic anhydride and maleic acid. It was recrystallized to constant melting point from ethanol. The purity of the compound was checked by elemental analysis and characterized by its infrared spectra.
Rod like colourless single crystals used in X-ray diffraction studies were grown in an ethanol solution by slow evaporation at room temperature.  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.