N-(3,5-Dimethylphenyl)succinamic acid

In the title compound, C12H15NO3, the N—H and C=O bonds are anti to each other. The C=O and O—H bonds of the acid group display an antiperiplanar orientation relative to each other. The crystal packing features a three-dimensional network of molecules held together by O—H⋯O and N—H⋯O hydrogen bonds.

In the title compound, C 12 H 15 NO 3 , the N-H and C O bonds are anti to each other. The C O and O-H bonds of the acid group display an antiperiplanar orientation relative to each other. The crystal packing features a three-dimensional network of molecules held together by O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds.
BSS thanks the University Grants Commission, Government of India, New Delhi, for the award of a research fellowship under its faculty improvement program.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT5440).

Comment
As a part of studying the effect of ring and side chain substitutions on the crystal structures of anilides (Gowda et al., 2009(Gowda et al., , 2010a, in the present work, the crystal structure of N-(3,5-dimethylphenyl)-succinamic acid (I) has been determined.
The conformations of N-H and C═ O bonds in the amide segment are anti to each other (Fig. 1). The conformation of the amide oxygen and the carbonyl oxygen of the acid segment are anti to each other, similar to the anti conformation observed in N-(2,6-dimethylphenyl)-succinamic acid (II) (Gowda et al., 2009), but in contrast to the the syn conformation observed in N-(3-methylphenyl)succinamic acid (III) (Gowda et al., 2010a) and N-(3,4-dimethylphenyl)-succinamic acid (IV) (Gowda et al., 2010b).
But, the conformations of the amide oxygen and the carbonyl oxygen of the acid segment are anti to the adjacent -CH 2 groups in the above compounds. The conformation of the amide hydrogen is syn to one of the meta-methyl groups in the benzene ring and anti to the other. The intermolecular O-H···O and N-H···O hydrogen bonds pack the molecules into a three-dimensional network (Table   1, Fig. 2).
The 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).

Experimental
The solution of succinic anhydride (0.01 mole) in toluene (25 ml) was treated dropwise with the solution of 3,5-dimethylaniline (0.01 mole) also in toluene (20 ml) with constant stirring. The resulting mixture was stirred for about one h and set aside for an additional hour at room temperature for completion of the reaction. The mixture was then treated with dilute hydrochloric acid to remove the unreacted 3,5-dimethylaniline. The resultant solid N-(3,5-dimethylphenyl)-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 ethanol. The purity of the compound was checked by elemental analysis and characterized by its infrared and NMR spectra.
Needle like colorless single crystals used in X-ray diffraction studies were grown in ethanolic solution by slow evaporation at room temperature.

Refinement
The H atoms of the NH and OH group were located in a difference map and their coordinates were refined. 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.  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.