Methyl N-(2,3-dichlorophenyl)succinamate

The asymmetric unit of the title compound, C11H11Cl2NO3, contains two independent molecules. In both the molecules, the H atoms of the adjacent –CH2 groups of the acid segments orient themselves away from the amide O and the carbonyl O atoms. The C=O and O—CH3 bonds of the ester group are in syn positions with respect to each other. In the crystal, the molecules are linked into infinite chains through intermolecular N—H⋯O hydrogen bonds.

The asymmetric unit of the title compound, C 11 H 11 Cl 2 NO 3 , contains two independent molecules. In both the molecules, the H atoms of the adjacent -CH 2 groups of the acid segments orient themselves away from the amide O and the carbonyl O atoms. The C O and O-CH 3 bonds of the ester group are in syn positions with respect to each other. In the crystal, the molecules are linked into infinite chains through intermolecular N-HÁ Á ÁO hydrogen bonds.   Table 1 Hydrogen-bond geometry (Å , ).

Experimental
The solution of succinic anhydride (0.02 mol) in toluene (25 ml) was treated dropwise with the solution of 3,4-dichloroaniline (0.02 mol) also in toluene (20 ml) with constant stirring. The resulting mixture was stirred for about one hour and set aside for an additional hour at room temperature for the completion of reaction. The mixture was then treated with dilute hydrochloric acid to remove the unreacted 3,4-dichloroaniline. The resultant solid N-(3,4-dichlorophenyl)succinamic acid was filtered under suction and washed thoroughly with water to remove the unreacted succinic anhydride and succinic acid.
It was recrystallized to constant melting point from methanol. Pure N-(3,4-dichlorophenyl)succinamic acid in methanol was refluxed with 2 ml of conc. sulfuric acid for two hours and was subjected to slow evaporation. The resulting N-(3,4dichlorophenyl)methylsuccinamate was recrystallised from methanol. The purity of the compound was checked and characterized by its infrared and NMR spectra.
Needle like colourless single crystals used in X-ray diffraction studies were grown in methanol solution by slow evaporation at room temperature.

Refinement
The H atoms of the NH groups were located in a difference map and their position refined with N-H = 0.86 (1) %A. The other H atoms were positioned with idealized geometry using a riding model with C-H = 0.93-0.97 Å. All H atoms were refined with isotropic displacement parameters (set to 1.2 times of the U eq of the parent atom). The U ij components of C11 and C22 were restrained to approximate isotropic behavoir.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq