Crystal structure of ethyl 2-{2-[(1Z)-1-hydroxy-3-(4-nitrophenyl)-3-oxoprop-1-en-1-yl]phenoxy}acetate

The title compound, C19H17NO7, crystallized in a ratio of about 6:4 of the two possible keto–enol forms. This was observed as disorder over the central C3H2O2 unit. The dihedral angle between the rings is 8.2 (2)°.The molecules pack by C—H⋯O interactions in a layered fashion parallel to (-104).


Related literature
Hydrogen-bond geometry (Å , ). In the title molecule, the dihedral angle between the C1-C6 ring and the mean plane of the central O3, C7, C8, C9, O4 unit is 2.8 (2)° while that between this latter plane and the C10-C15 ring is 8.2 (2)°. The molecule crystallized as a mixture of the two possible keto enol forms. This was observed as disorder over the central C 3 H 2 O 2 unit. The molecules pack in a layered fashion (Figs. 2 and 3).

S2. Experimental
The title compund was prepared according to our reported method (Akkurt et al., 2015). Suitable crystals were obtained by slow evaporation method of a solution of the title compund in ethanol.

S3. Refinement
H-atoms attached to carbon were placed in calculated positions (C-H = 0.95 -0.99 Å). All were included as riding contributions with isotropic displacement parameters 1.2 -1.5 times those of the attached atoms. From the equivalence of the C7-C8 and C8-C9 bond distances, the near equivalence of the C7-O3 and C9-O4 bond distances and the observance of only one peak attributable to a hydrogen attached to C8 in a difference map, it was concluded that the compound exists as the keto-enol tautomer with the enol hydrogen disordered between O3 and O4. Contoured difference maps calculated in the region between O3 and O4 showed an elongated region of density consistent with this assumption.
The two components of the disordered hydrogen (H3a and H4a) were placed in positions consistent with forming intramolecular O-H···O hydrogen bonds and allowed to ride on the respective oxygen atoms.

Figure 1
The title molecule with labeling scheme and 50% probability ellipsoids. Only one location (H4A) of the disordered enol hydrogen is shown. Intramolecular hydrogen bonds are shown by dotted lines.

Figure 2
Packing viewed down the a axis. Intermolecular C-H···O hydrogen bonds are shown by dotted lines.

Figure 3
Packing viewed down the b axis showing the layered structure.  are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. H-atoms attached to carbon were placed in calculated positions (C-H = 0.95 -0.99 Å). All were included as riding contributions with isotropic displacement parameters 1.2 -1.5 times those of the attached atoms. From the equivalence of the C7-C8 and C8-C9 bond distances, the near equivalence of the C7-O3 and C9-O4 bond distances and the observance of only one peak attributable to a hydrogen attached to C8 in a difference map, it was concluded that the compound exists as the keto-enol tautomer with the enol hydrogen disordered between O3 and O4. Contoured difference maps calculated in the region between O3 and O4 showed an elongated region of density consistent with this assumption. The two components of the disordered hydrogen (H3a and H4a) were placed in positions consistent with forming intramolecular O-H···O hydrogen bonds and allowed to ride on the respective oxygen atoms.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (