Crystal structure of 2-hydroxy-2-phenylacetophenone oxime

The phenyl rings are almost oriented perpendicularly. In the crystal, intermolecular O—HOxm⋯NOxm, O—HHydr⋯OHydr, O—H′Hydr⋯OHydr and O—HOxm⋯OHydr hydrogen bonds link the molecules into infinite chains along the c-axis direction.

The title compound [systematic name: 2-(N-hydroxyimino)-1,2-diphenylethanol], C 14 H 13 NO 2 , consists of hydroxy phenylacetophenone and oxime units, in which the phenyl rings are oriented at a dihedral angle of 80.54 (7) . In the crystal, intermolecular O-H Oxm Á Á ÁN Oxm , O-H Hydr Á Á ÁO Hydr , O-H 0 Hydr Á Á Á O Hydr and O-H Oxm Á Á ÁO Hydr hydrogen bonds link the molecules into infinite chains along the c-axis direction.contacts between inversion-related of the phenyl ring adjacent to the oxime group have a centroid-centroid separation of 3.904 (3) Å and a weak C-HÁ Á Á(ring) interaction is also observed. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from HÁ Á ÁH (58.4%) and HÁ Á ÁC/CÁ Á ÁH (26.4%) contacts. Hydrogen bonding and van der Waals contacts are the dominant interactions in the crystal packing.

Chemical context
Intermolecular hydrogen bonding has received considerable attention among the directional non-covalent intermolecular interactions (Etter et al., 1990). Hydrogen bonds combine moderate strength and directionality (Karle et al., 1996) in linking molecules to form supramolecular structures. The oxime (-C N-OH) moiety, which is similar to carboxylic acid in that it contains one hydrogen-bond donor and two acceptor atoms, is a functional group that has not been extensively explored in crystal engineering. Structurally characterized oxime moieties are much less common than carboxylic acids and amides, but from a supramolecular perspective, this functionality does have some unique and desirable features (Aakerö y et al., 2001). Oxime groups possess stronger hydrogen-bonding capabilities than alcohols, phenols and carboxylic acids (Marsman et al., 1999). The hydrogen-bond systems in the crystals of oximes have been analysed and a correlation between patterns of hydrogen bonding and N-O bond lengths has been suggested (Bertolasi et al., 1982). Oxime and dioxime derivatives are very important in the chemical industry, photography, agriculture, textiles, technological improvement, dye chemistry, semiconductor manufacturing and medicine (Sevagapandian et al., 2000;Schrauzer et al., 1965;Thomas & Underhill, 1972;Underhill et al., 1973;Chakravorty, 1974;Kurita, 1998;Mathur & Narang, 1990;Ravi Kumar, 2000). They have a broad pharmacological activity spectrum, encompassing antibacterial, antidepressant and antifungal activities (Forman, 1964;Holan et al., 1984). Some oxime complexes also have anticarcinogenic activities (Sevagapandian et al., 2000;Srivastava et al., 1997). The crystallization and the molecular ISSN 2056-9890 and crystal structures of the title compound, (I), are reported herein. Its magnetic properties have previously been studied by electron paramagnetic resonance (EPR) (Sayin et al., 2012).

Synthesis and crystallization
The alpha-benzoinoxime [ABO (C 14 H 13 NO 2 ) powder was purchased from Merck, and crystallized by slow evaporation from a concentrated solution in ethanol as colourless crystals at room temperature.  Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
A partial packing diagram.  The asymmetric unit of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. The hydrogen attached to hydroxyl oxygen O2 is disordered in a 50:50 ratio, as indicated by dashed bonds.

Figure 3
A packing diagram viewed down the c axis.  (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: WinGX publication routines (Farrugia, 2012) and PLATON (Spek, 2020). 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.