N-(3-Nitrophenyl)maleamic acid

In the title compound, C10H8N2O5, the molecule is slightly distorted from planarity. The molecular structure is stabilized by two intramolecular hydrogen bonds. The first is a short O—H⋯O hydrogen bond (H⋯O distance = 1.57 Å) within the maleamic acid unit and the second is a C—H⋯O hydrogen bond (H⋯O distance = 2.24 Å) which connects the amide group with the benzene ring. The nitro group is twisted by 6.2 (2)° out of the plane of the benzene ring. The crystal structure manifests a variety of hydrogen bonding. The packing is dominated by a strong intermolecular N—H⋯O interaction which links the molecules into chains running along the b axis. The chains within a plane are further assembled by three additional types of intermolecular C—H⋯O hydrogen bonds to form a sheet parallel to the (01) plane.

In the title compound, C 10 H 8 N 2 O 5 , the molecule is slightly distorted from planarity. The molecular structure is stabilized by two intramolecular hydrogen bonds. The first is a short O-HÁ Á ÁO hydrogen bond (HÁ Á ÁO distance = 1.57 Å ) within the maleamic acid unit and the second is a C-HÁ Á ÁO hydrogen bond (HÁ Á ÁO distance = 2.24 Å ) which connects the amide group with the benzene ring. The nitro group is twisted by 6.2 (2) out of the plane of the benzene ring. The crystal structure manifests a variety of hydrogen bonding. The packing is dominated by a strong intermolecular N-HÁ Á ÁO interaction which links the molecules into chains running along the b axis. The chains within a plane are further assembled by three additional types of intermolecular C-HÁ Á ÁO hydrogen bonds to form a sheet parallel to the (101) plane.

Comment
In the present study, 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,c;Prasad et al., 2002), the crystal structure of N-(3-nitrophenyl)maleamic acid (I) has been determined ( Fig. 1). The conformation of the N-H in the amide segment is anti to the C=O bond and is also anti to the meta-nitro 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 obsrved in N-(2-methylphenyl)-maleamic acid (Gowda et al., 2010b), N-(3-chlorophenyl)-maleamic acid (Gowda et al., 2010c) and N-(3,5-dichlorophenyl)-maleamic acid (Gowda et al., 2010a).
The molecule in (I) is slightly distorted from planarity as indicated by the dihedral angle of 4.5 (1)° between the least squares planes of the maleamic acid unit (r.m.s. deviation of 0.050 Å) and the phenyl ring. The molecular structure ( Fig. 1) is stabilized by two intramolecular hydrogen bonds (Table 1). The first is a short O-H···O hydrogen bond ((H···O distance of 1.57 Å) within the maleamic acid unit; the second one is a C-H···O hydrogen bond (H···O distance of 2.24 Å) which connects the amide group with the phenyl ring. The nitro group -known to be a strong electron-withdrawing substituent -opens up the ipso C-C-C angle and narrows the two adjacent intracyclic angles. This fact is evident from the intracyclic bond angles C6-C7-C8, C5-C6-C7 and C7-C8-C9 of 123.99 (12)°, 117.49 (12)° and 117.64 (12)° respectively. The nitro group is twisted 6.2 (2)° out of the plane of the phenyl ring.
The crystal structure (Fig. 2) manifests a variety of hydrogen bonding. The packing is dominated by a strong intermolecular N-H···O interaction (H···O distance of 2.05 Å) which links the molecules into the chains running along the b axis. The chains within a plane are further assembled by additional three types of intermolecular C-H···O hydrogen bonds to form a sheet parallel to the (-1 0 1) plane (Bernstein et al., 1995).

Experimental
The solution of maleic anhydride (0.025 mol) in toluene (25 ml  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.