Ethyl (2Z)-3-hydroxy-3-(4-nitrophenyl)prop-2-enoate

The title compound, C11H11NO5, is essentially planar, with an r.m.s. deviation of 0.06 Å. The molecular structure is stabilized by an intramolecular O—H⋯O hydrogen bond. In the crystal, molecules are linked by two pairs of C—H⋯O hydrogen bonds, forming sheets, lying parallel to (101), which enclose R 4 4(26) ring motifs.

The University of the Witwatersrand and the Molecular Sciences Institute are thanked for providing the infrastructure and financial support. Special thanks go to Dr Andreas Lemmerer of the University of the Witwatersrand for his contributions and insights toward this project.
Supporting information for this paper is available from the IUCr electronic archives (Reference: BX2458).

Comment
The molecular structure of (I) is illustrated in Figure 1, and was obtained by recrystallization of the commercially available compound. The title compound, C 11 H 11 NO 5 , consists of a hydroxy (O1) and a p-nitrophenyl substituted propenoate.The molecule is essentially planar with an r.m.s. deviation of 0.065Å, the larger r.m.s. value is as a result of the slight twisting of the substituents on the propenoate backbone, the dihedral angle of the planes of the subsitutents with the propenoate plane were found to be 3.69 (4) ° for the p-nitrophenyl and 3.3 (1) ° for the ethyl ester.
The propenoate backbone was observed in the enol tautomeric form with a typical hydrogen bond interaction between the hydroxy (O1) and the carbonyl (O2) with a distance of 2.603 (2) Å. The packing of (I) is seen as parallel sheets ( Figure 2) when viewed along the b-axis. The crystal and molecular structure is stabilized by two weak C-H···O hydrogen bond interactions with graph-set motif R 4 4 (26) (Bernstein, et al., 1995) and one O-H···O intramolecular hydrogen bond interaction respectively, Table 1 2

. Experimental
Ethyl 4-nitrobenzoylacetate was obtained commercially. (I) It was redissolved in warm MeOH and allowed to cool to room terperature. Yellow crystals suitable for single-crystal diffraction were obtained by slow evaporation over a few days.

Refinement
All hydrogen atoms were positioned geometrically and refined using a riding model, with C-H = 0.95 Å U iso (H)= 1.2 U eq (C) for the aromatic H atoms, with C-H = 0.98 Å U iso (H)= 1.5 U eq (C) for methyl H atoms and with O-H = 0.84 Å U iso (H)= 1.5 U eq (O) for the hydroxyl H atoms. The methyl and hydroxyl groups were allowed to rotate with a fixed angle arround the C-C bond to best fit the experimental electron density [HFIX 137 and HFIX 147 in SHELXL97 (Sheldrick, 2008)].  Molecular structure of (I), showing the atom labelling scheme and displacement ellipsoids at 20% probability level.
(arbitrary spheres for the H atoms)

Figure 2
Packing of (I) viewed along the b-axis. Hydrogen atoms omitted for clarity.