N-(2,5-Dimethylphenyl)succinamic acid monohydrate

In the title compound, C12H15NO3·H2O, the conformation of the N—H bond in the amide segment is syn to the ortho-methyl group and anti to the meta-methyl group in the benzene ring. Further, the conformations of the amide O and the carbonyl O atom of the acid segment are anti to the adjacent methylene H atoms. The C=O and O—H bonds of the acid group are syn to one another. The structure shows an interesting hydrogen-bonding pattern with the water molecule forming hydrogen bonds with three different molecules of the compound. In the crystal, molecules are packed into infinite chains through intermolecular O—H⋯O and N—H⋯O hydrogen bonds.

In the title compound, C 12 H 15 NO 3 ÁH 2 O, the conformation of the N-H bond in the amide segment is syn to the orthomethyl group and anti to the meta-methyl group in the benzene ring. Further, the conformations of the amide O and the carbonyl O atom of the acid segment are anti to the adjacent methylene H atoms. The C O and O-H bonds of the acid group are syn to one another. The structure shows an interesting hydrogen-bonding pattern with the water molecule forming hydrogen bonds with three different molecules of the compound. In the crystal, molecules are packed into infinite chains through intermolecular 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.

Comment
The amide and sulfonamide molecules are important constituents of many biologically important compounds. As a part of our studies of the substituent effects on the structures and other aspects of this class of compounds (Gowda et al., 1999(Gowda et al., , 2000(Gowda et al., , 2010aSaraswathi et al., 2011), in the present work, the crystal structure of N-(2,5-dimethylphenyl)-succinamic acid monohydrate (I) has been determined ( Fig. 1). The conformation of the N-H bond in the amide segment is syn to the ortho-methyl group and anti to the meta-methyl group in the benzene ring, similar to the syn conformation observed between the amide hydrogen and the ortho-methyl group in N-(2-methylphenyl)succinamic acid (II) (Gowda et al., 2010b) and the anti conformation observed between the amide hydrogen and the meta-methyl group in the benzene ring of N-(3methylphenyl)succinamic acid (III) (Gowda et al., 2010a). The conformation of the amide oxygen and the carbonyl oxygen of the acid segment are anti to each other. Further, the conformations of these are anti to the adjacent methylene H-atoms.
The C═O and O-H bonds of the acid group are in syn position to each other, similar to that observed in (II) and (III).
The structure shows interesting H-bond pattern with water molecule forming H-bonding with three different molecules of the compound. Intermolecular O-H···O and N-H···O hydrogen bonds pack the molecules into infinite chains in the structure (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
A solution of succinic anhydride (0.01 mole) in toluene (25 ml) was treated dropwise with the solution of 2,5-dimethylaniline (0.01 mole) 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 completion of the reaction. The mixture was then treated with dilute hydrochloric acid to remove the unreacted 2,5-dimethylaniline. The resulting title compound 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 and characterized by its infrared and NMR spectra.
Colorless needle like 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 gorup and the water molecule were located in a difference map and their position refined with 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.