Crystal structure of N-(2-hydroxyethyl)-5-nitroisophthalamic acid monohydrate

In the title compound, C10H10N2O6·H2O, the carboxylic acid group and the nitro group are essentially coplanar with the benzene ring [maximum deviation = 0.0264 (9) Å], while the amide group is oriented at a dihedral angle of 9.22 (5)° with respect to the benzene ring. In the crystal, classical O—H⋯O and N—H⋯O hydrogen bonds and weak C—H⋯O interactions link the organic molecules and water molecules of crystallization into a three-dimensional supramolecular architecture.


Related literature
The title compound is an intermediate for the preparation of iodinated X-ray contrast media, such as ioxitalamic acid and ioxilan, see: Prous et al. (1995); Sovak (1988); Stacul (2001). For a related structure, see: Liu et al. (2009 Table 1 Hydrogen-bond geometry (Å , ). Pei Zou, Hong-Yong Wang, Shi-Neng Luo, Ya-Ling Liu and Yong-Jia Shen S1. Comment The title compound has been used as an important intermediate for the preparation of iodinated X-ray contrast media, such as ioxitalamic acid and ioxilan, which are used clinically all over the world (Prous et al., 1995;Sovak et al., 1988;Stacul et al., 2001). We report here the crystal structure of title compound.
The structure of the title compound is shown in Fig. 1 and hydrogen bond geometry is given in Table 1. The crystal data show that the bond lengths and angles are within expected ranges and agree well with the corresponding molecular dimensions reported for a similar compound (Liu et al., 2009) . In the title compound, the carboxylic acid group and nitro group are approximately co-planar with the benzene ring [maximum deviation = 0.0264 (9) Å], while the amide moiety is oriented with respect to the benzene ring at 9.22 (5)°. In the crystal, classic O-H···O, N-H···O hydrogen bonds and weak C-H···O hydrogen interactions link organic molecules and crystalline water molecules into the three dimensional supramolecular architecture.

S2. Exprimental
Monomethyl 5-nitrobenzene-1,3-dihydrogencarboxylate (900 mg, 4 mmol) was dissolved in methanol (5 ml), then ethanolamine (610 mg, 10 mmol) was added and the mixture was refluxed for 16 h. Methanol was distilled off. The residue was dissolved in water and methanol (v/v 1:1), then acidified with 1 M hydrochloric acid to pH = 3. The precipitate was filtered and washed with water. The crude product was recrystallized from ethanol/water. Single crystals were obtained by slow evaporation of an ethanol/water (v/v 7:1) solution.

S3. Refinement
Hydroxyl H, water H and amino H atoms were located in a difference Fourier map and refined isotropically. Other H atoms were placed in calculated positions with C-H = 0.95-0.99 Å, and refined in riding mode, U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for the others.  A view of the title compound with the atomic numbering scheme. Displacement ellipsoids were drawn at the 30% probability level.

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