N-(4-Methylphenyl)succinamic acid

In the title compound, C11H13NO3, the conformations of the N—H and C=O bonds in the amide segment are anti to each other. Further, the conformations of the amide and carbonyl O atoms of the acid segment are also anti to the adjacent –CH2 groups. The C=O and O—H bonds of the acid group are syn to each other. In the crystal, molecules are packed into infinite chains along the b axis through intermolecular N—H⋯O and O—H⋯O hydrogen bonds.

In the title compound, C 11 H 13 NO 3 , the conformations of the N-H and C O bonds in the amide segment are anti to each other. Further, the conformations of the amide and carbonyl O atoms of the acid segment are also anti to the adjacent -CH 2 groups. The C O and O-H bonds of the acid group are syn to each other. In the crystal, molecules are packed into infinite chains along the b axis through intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds.

Related literature
For background to our study of the effect of ring and sidechain substitution on the solid state geometry of anilides, see: Gowda et al. (2009Gowda et al. ( , 2010a. For modes of interlinking carboxylic acids by hydrogen bonds, see: Leiserowitz (1976). The packing of molecules involving dimeric hydrogen-bonded association of each carboxyl group with a centrosymmetrically related neighbor has also been observed, see: Jagannathan et al. (1994).  Table 1 Hydrogen-bond geometry (Å , ).

Comment
In the present work, as a part of studying the effect of ring and side chain substitutions on the solid state geometry of anilides (Gowda et al., 2009(Gowda et al., , 2010a, the crystal structure of N-(4-methylphenyl)-succinamic acid (I) has been determined. The conformations of N-H and C=O bonds in the amide segment are anti to each other. The conformation of the amide oxygen and the carbonyl oxygen of the acid segment are also anti to each other, similar to that observed in N-(4-Chlorophenyl)succinamic acid (II) (Gowda et al., 2009) and N-(2-methylphenyl)-succinamic acid (III) (Gowda et al., 2010b). but contrary to the syn conformation observed in N-(3-methylphenyl)-succinamic acid (IV) (Gowda et al., 2010a). 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 p-toluidine (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 p-toluidine. The resultant solid N-(4-methylphenyl)-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.
The plate 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 group and OH group were located in a difference map and later restrained to the distance N-H   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.