Cystal structre of 5-hydroxy-2-nitrobenzaldehyde

In the title compound, C7H5NO4, the nitro group and the aldehyde group are inclined to the benzene ring by 16.6 (3) and 15.6 (3)°, respectively. In the crystal, molecules are linked via O—H⋯O hydrogen bonds, forming chains along [100]. The chains are linked by C—H⋯O hydrogen bonds, forming a three-dimensional structure.


S2. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The hydroxyl H atom was located in a difference Fourier map and freely refined. The C-bound H atoms were positioned geometrically and constrained to ride on their parent atoms: C-H = 0.93 Å, with U iso (H) = 1.2U eq (C).

S3. Comment
Nitro substituted aromatic compounds are well known intermediates in various organic reactions, responsible for synthesis of pesticides, explosive materials and other bioactive phenyl derivatives (Yan et al., 2006). The nitro substituted aromatic compounds are also known to be widely distributed as pollutant in air and water reservoirs (Yan et al., 2006;Soojhawon et al., 2005). The title compound is a commercially available benzaldehyde derivative, composed of a planar hydroxy substituted nitrobenzaldehyde ring. The compound was crystal out as a part of our ongoing research project involving to crystallize and evaluate biological activities of commercially available molecular libraries.
The molecular structure of the title compound is illustrated in Fig. 1. Structurally it is a positional isomer of the previously reported 2-hydroxy-5-nitrobenzaldehyde with the difference that the positions of the hydroxy and nitro substituents are interchanged (Tanak et al., 2009). The nitro group (N1/O1/O2) and the aldehyde group (C6/C1/O4) are inclined to the benzene ring (C1-C6) by 16.6 (3) and 15.6 (3) °, respectively.
In the crystal, molecules are linked by O-H···O hydrogen bonds forming zigzag chains along [100]. The chains are linked via C-H···O hydrogen bonds forming a three dimensional structure (Table 2 and Fig. 2).

Figure 1
The molecular structure of title compound, with atom labelling. Displacement ellipsoids are drawn at 30% probability level.

Figure 2
The crystal packing of title compound, viewed along the b axis. Hydrogen bonds are shown as dashed lines (see Table 1 for details). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.19 e Å −3 Δρ min = −0.16 e Å −3 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.