(E)-4-Methoxy-N′-(2,4,5-trimethoxybenzylidene)benzohydrazide hemihydrate

The title compound crystallizes as a hemihydrate, C18H20N2O5·0.5H2O. The molecule exists in an E conformation with respect to the C=N imine bond. The 4-methoxyphenyl unit is disordered over two sets of sites with a refined occupancy ratio of 0.54 (2):0.46 (2). The dihedral angles between the benzene rings are 29.20 (9) and 26.59 (9)°, respectively, for the major and minor components of the 4-methoxy-substituted ring. All methoxy substituents lie close to the plane of the attached benzene rings [the Cmethyl—O—C—C torsion angles range from −4.0 (12) to 3.9 (2)°]. In the crystal, the components are linked into chains propagating along [001] via N—H⋯O and O—H⋯O hydrogen bonds and weak C—H⋯O interactions.

The title compound crystallizes as a hemihydrate, C 18 H 20 N 2 O 5 Á0.5H 2 O. The molecule exists in an E conformation with respect to the C N imine bond. The 4-methoxyphenyl unit is disordered over two sets of sites with a refined occupancy ratio of 0.54 (2):0.46 (2). The dihedral angles between the benzene rings are 29.20 (9) and 26.59 (9) , respectively, for the major and minor components of the 4methoxy-substituted ring. All methoxy substituents lie close to the plane of the attached benzene rings [the C methyl -O-C-C torsion angles range from À4.0 (12) to 3.9 (2) ]. In the crystal, the components are linked into chains propagating along [001] via N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds and weak C-HÁ Á ÁO interactions.  (2012). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 Table 1 Hydrogen-bond geometry (Å , ).

Comment
Benzohydrazide derivatives and their complexes have been found to exhibit various biological properties, such as analgesic, antifungal and antibacterial (Raj et al., 2007 andWang et al., 2012 ), including antioxidant and biocidal activities (Sathyadevi et al., 2012). In contiuation of our on-going research on the bioactivity of benzohydrazides, the title compound (I) was synthesized and evaluated for antioxidant activity by DPPH free radical scavenging method (Molyneux, 2004), but was found to be inactive. It was also screened for antibacterial activity against B. subtilis, S. aureus, P. aeruginosa, S. typhi and S. sonnei and also found to be inactive. Herein we report the synthesis and crystal structure of (I).
The asymmetric unit of (I) (Fig. 1) consists of a C 18 H 20 N 2 O 5 molecule and half an H 2 O molecule. The 4-methoxyphenyl unit is disordered over two positions with a refined site-occupancy ratio of 0.538 (2):0.462 (2). The benzohydrazide exists in an E configuration with respect to the C8═N2 imine bond [1.285 (2)Å] and the N1-N2-C8-C9 torsion angle is 178.38 (15)°. The molecule is twisted with a dihedral angle between the two substituted benzene rings being 29.20 (9) and 26.59 (9)° for the major A and minor B components, respectively. Five atoms (O1, C7, N1, N2 and C8) of the middle bridge fragament lie on the same plane with the r.m.s. deviation of 0.0187 (2) Å. The mean plane through this middle fragment makes the dihedral angles of 22.67 (9) and 19.51 (9)° with the C1-C6 benzene ring for the major A and minor B components, respectively, and 6.84 (10)° with the C9-C14 benzene ring. The methoxy substituent of 4-methoxyphenyl lies close to the plane of the attached benzene ring with the torsion angle C15-O2-C4-C5 = 0.1 (11)° and the r.m.s. In the crystal packing (Fig. 2), the benzohydrazide and water molecules are linked by O-H···O, N-H···O hydrogen bonds and weak C-H···O interactions (Table 1)

Experimental
The title compound (I) was prepared by dissolving 4-methoxybenzohydrazide (2 mmol, 0.30 g) in ethanol (10 ml). The solution of 2,4,5-trimethoxybenzaldehyde (2 mmol, 0.40 g) in ethanol (10 ml) was then added slowly to commence the reaction. The reaction mixture was refluxed for around 3 hr. The solution was then cooled to room temperature yielding a white solid, which was collected by filtration, washed with ethanol and dried in air. Colorless plate-shaped single crystals of the title compound suitable for X-ray structure determination were recrystallized from ethanol by slow evaporation of the solvent at room temperature after several days.

Refinement
The amide H atom was located a the difference map was refined freely. The remaining H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(O-H) = 0.85 Å, d(C-H) = 0.93 Å for aromatic and C-H and 0.96 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 groups. The 4-methoxyphenyl unit is disordered over two sites with refined site occupancies ratio 0.538 (2):0.462 (2). Similarity and simulation restraints were applied. The thermal ellipsoids of each pair of atoms i.e. "C1A C1B", "C2A C2B", "C5A C5B" and "C6A C6B" were restrained to be equal.    The crystal packing viewed along the b axis showing hydrogen bonds drawn as dashed lines. Only the major component of disorder is shown.

Special details
Experimental. The data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. 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. 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 > 2sigma(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.