N-(4-Hydroxy-2-nitrophenyl)acetamide

The title compound is more planar than its 3-nitro isomer in the solid state and differs in its hydrogen-bonding pattern.

Towards a better understanding of this chemistry, we have synthesized N-(4-hydroxy-2-nitrophenyl)acetamide and N-(4-hydroxy-3-nitrophenyl)acetamide and determined their single-crystal structures. Interestingly, the 2-nitro and 3-nitro isomers have signifi-data reports cantly different degrees of molecular planarity in the solidstate and also differ in their hydrogen bonding patterns.
In N-(4-hydroxy-2-nitrophenyl)acetamide, Fig. 1, the molecule is nearly planar, with an r.m.s. deviation of 0.035 Å for the non-hydrogen atoms. The acetamido group has the largest deviation, with a 5.1 (2) twist about its central C7-N2 bond. The N-H group forms an intramolecular hydrogen bond (Table 1)  The crystal structure of N-(4-hydroxy-3-nitrophenyl)acetamide has been reported (Salahifar et al., 2015;Deere et al., 2019). It is significantly less planar than the title compound, with the acetamido group twisted out of the plane of the phenyl group by 9.0 (2) and the nitro group twisted out of the phenyl plane by 11.8 (2) . Its hydrogen-bonding pattern also differs, with the N-H group forming an intermolecular

Figure 2
The hydrogen-bonded chain.

Figure 3
The unit cell of the title compound.

Figure 1
The molecular structure of the title molecule with 50% displacement ellipsoids.
data reports Hines III et al.
added to the mixture with the contents being constantly stirred. Care was taken to maintain that the pH of the final reaction mixture was between 5.5 and 6.5. The yellow precipitate of N-(4-hydroxy-2-nitrophenyl)acetamide was separated by filtration and purified by recrystallization twice from aqueous solution. Single crystals were grown from methanol solution.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

Funding information
The authors acknowledge the support from the National Institutes of Health (  Schematic representation of the synthesis of the title compound.

N-(4-Hydroxy-2-nitrophenyl)acetamide
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.29 e Å −3 Δρ min = −0.23 e Å −3 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. All H atoms were located in difference maps and those on C were thereafter treated as riding in geometrically idealized positions with C-H distances 0.95 Å for phenyl and 0.98 Å for methyl. The coordinates of the N -H and O-H hydrogen atoms were refined. U iso (H) values were assigned as 1.2U eq for the attached atom (1.5 for OH and methyl).