4-[(E)-(4-Ethoxybenzylidene)amino]phenol

The molecule of the title compound, C15H15NO2, adopts a trans conformation with respect to the methylidene C=N bond and is twisted with a dihedral angle of 26.31 (5)° between the two substituted benzene rings. The ethoxy group is almost coplanar with the bound benzene ring with a C—O—C—C torsion angle of −179.08 (9)°. In the crystal, molecules are linked by O—H⋯N hydrogen bonds and weak C—H⋯O interactions into chains propagating in the [011] and [01-1] directions. C—H⋯π interactions are also present.

The molecule of the title compound, C 15 H 15 NO 2 , adopts a trans conformation with respect to the methylidene C N bond and is twisted with a dihedral angle of 26.31 (5) between the two substituted benzene rings. The ethoxy group is almost coplanar with the bound benzene ring with a C-O-C-C torsion angle of À179.08 (9) . In the crystal, molecules are linked by O-HÁ Á ÁN hydrogen bonds and weak C-HÁ Á ÁO interactions into chains propagating in the [011] and [011] directions. C-HÁ Á Á interactions are also present.

4-[(E)-(4-Ethoxybenzylidene)amino]phenol
Narissara Kaewmanee, Suchada Chantrapromma, Nawong Boonnak and Hoong-Kun Fun Comment Aza-stilbene derivatives derived from the reaction of an aldehyde with hydrazine have been shown to possess potent biological activities such as antibacterial (Kabir et al., 2008), antifungal (da Silva et al., 2011), antimycobacterium tuberculosis (Pavan et al., 2011) and antioxidation (Cheng et al., 2010;Lu et al., 2012) properties. These interesting biological activities of aza-stilbene led us to synthesize the title compound, (I), and study its antibacterial activity. Our antibacterial assay showed that (I) exhibits moderate activity against Salmonella typhi with the minimun inhibition concentration (MIC) value of 18.75 µg/ml. We report here the crystal structure of the title compound.
The molecule of (I) (Fig. 1), C 15 H 15 NO 2 , is twisted and exists in a trans configuration with respect to the methylidene C7═N1 double bond [1.2867 (13) Å] with the torsion angle C8-N1-C7-C1 = 179.23 (8)°. The dihedral angle between the two substituted benzene rings is 26.31 (5)°. The ethoxy group is co-planar with the bound benzene ring with the r.m.s. deviation of 0.0155 (1) Å for the nine non H-atoms and the C4-O1-C14-C15 angle is -179.08 (9)°. The bond distances are within the normal range (Allen et al., 1987) and are in agreement with those reported for related structures (Sun et al., 2011;Wang, 2009).
In the crystal structure (Fig. 2), the molecules are linked by O-H···N hydrogen bond and weak C-H···O interactions (Table 1) (Table 1).

Experimental
The title compound (I) was prepared by dissolving 4-benzylideneaniline (5 mmol, 0.50 g) in ethanol (30 ml) and 4-ethoxybenzaldehyde (5 mmol, 0.70 ml) was slowly added with stirring. The solution was stirred at room temperature for around 3 hr yielding a white solid, which was filtered off and washed with cold ethanol and dried in air. Colourless blockshaped single crystals of (I) suitable for X-ray structure determination were recrystallized from methanol by slow evaporation at room temperature after several days, M. p. 470-472 K.

Refinement
The hydroxyl H atom was located in a difference map and refined isotropically. The remaining H atoms were fixed geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.95 Å for aromatic and CH, 0.99 Å for CH 2 and 0.98 Å for CH 3 atoms. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl group. 1762 Friedel pairs were merged as there is insufficient anomalous dispersion to determine the absolute structure since Mo radiation was used for data collection.

Figure 1
The asymmetric unit of the title compound showing 65% probability displacement ellipsoids.  Special details Experimental. The data was collected with the Oxford Cryosystem Cobra low-temperature attachment. 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.