2-Ethyl-1H-imidazole-4-carboxylate monohydrate

In the title compound, C7H8N2O4·H2O, the imidazole N atom is protonated and one of the carboxylate groups is deprontonated, forming a zwitterion. The two carboxyl groups are are approximately coplanar with the imidazole ring [O—C—C—C torsion angles = −176.8 (2) and 2.9 (4)° for one group and −4.6 (3) and 176.4 (2)° for the other] and have an intramolecular O—H⋯O hydrogen bond between them. The water molecule is linked to the organic molecules via an N—H⋯O hydrogen bonds. Intermolecular O—H⋯O and N—H⋯O hydrogen bonds are found in the crystal structure.

In the title compound, C 7 H 8 N 2 O 4 ÁH 2 O, the imidazole N atom is protonated and one of the carboxylate groups is deprontonated, forming a zwitterion. The two carboxyl groups are are approximately coplanar with the imidazole ring [O-C-C-C torsion angles = À176.8 (2) and 2.9 (4) for one group and À4.6 (3) and 176.4 (2) for the other] and have an intramolecular O-HÁ Á ÁO hydrogen bond between them. The water molecule is linked to the organic molecules via an N-HÁ Á ÁO hydrogen bonds. Intermolecular O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds are found in the crystal structure.
However, the crystal structure of H 3 EIDC ligand has not been determined. Considering that in mind, we focus on obtaining the crystal and its crystal structure will be reported here.

Experimental
The organic molecule powder was abtained from 2-ethylbenzimidazole according to a literature procedure (Sun et al. 2006), then the 2-ethyl-1H-imidazole-4,5-dicarboxylate(0.5 mmol, 0.9 g) was disolved in 15 ml of H 2 O solution with the pH of 6 adjusted by NaOH, colorless crystals was obtained by slow evaporation of the solvent at room temperature.

Refinement
H atoms of the water molecule were located in a difference Fourier map and refined as riding with an O-H distance restraint of 0.84 (1) Å, with U iso (H) = 1.5 U eq . The H···H distances within the water molecules were restraint to 1.39 (1)

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 > 2sigma(F 2 ) is used only for calculating R-factors(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 )