(E,E)-1-(2-Hydroxyimino-1-phenylethylidene)semicarbazide monohydrate

In the title compound, C9H10N4O2·H2O, the oxime unit has an E configuration, and an intramolecular N—H⋯N hydrogen bond results in the formation of a planar five-membered ring, which is oriented with respect to the aromatic ring at a dihedral angle of 74.82 (17)°. In the crystal structure, intermolecular O—H⋯O and N—H⋯O hydrogen bonds link the molecules and R 2 2(8) ring motifs are apparent.

In the title compound, C 9 H 10 N 4 O 2 ÁH 2 O, the oxime unit has an E configuration, and an intramolecular N-HÁ Á ÁN hydrogen bond results in the formation of a planar five-membered ring, which is oriented with respect to the aromatic ring at a dihedral angle of 74.82 (17) . In the crystal structure, intermolecular O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds link the molecules and R 2 2 (8) ring motifs are apparent.

Comment
Oxime and dioxime derivatives have a broad pharmacological activity spectrum, encompassing antibacterial, antidepressant and antifungal activities (e.g. Balsamo et al., 1990). The oxime (-C=N-OH) moiety is potentially ambidentate, with possibilities of coordination to metal ions through nitrogen and/or oxygen atoms. Oxime groups possess stronger hydrogenbonding capabilities than alcohols, phenols, and carboxylic acids (Marsman et al., 1999), in which intermolecular hydrogen bonding combines moderate strength and directionality (Karle et al., 1996) in linking molecules to form supramolecular structures; this has received considerable attention with respect to directional noncovalent intermolecular interactions (Etter et al., 1990).
The structures of some oxime and dioxime derivatives have been determined in our laboratory, including those of 2,3- As part of our ongoing studies in this area, the structure determination of the title compound, (I), an oxime derivative with one semicarbazide, one phenylacetaldehyde oxime moieties and one uncoordinated water molecule, was carried out in order to investigate the strength of the hydrogen bonding capability of the oxime and semicarbazide groups and to compare the geometry of the oxime moiety with the previously reported ones.

Experimental
Semicarbazide hydrochloride (1.12 g, 10 mmol) and sodium acetate (0.82 g, 10 mmol) were dissolved in double distilled water in the molar ratio 1:1. Then, the solution was mixed with a solution of 2-isonitrosoacetophenone (1.49 g, 10 mmol) in ethanol (10 ml) yielding a turbid mixture. The excess ethanol was added to get a clear solution and was stirred in a magnetic stirrer at room temparature for 4 h. The precipitate formed was filtered, washed with water and dried at room temperature supplementary materials sup-2 in vacuum desiccator. It was recrystallized from ethanol/water (2:1) solution to yield colourless prisms of (I) (yield; 1.80 g, 85%, m.p. 409 K).

Special details
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 Rfactors(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.  (7) 2.909 (11) 140 (7) N2-H22···O3 ii 0.82 (3) 2.10 (4) 2.901 (10) 162 (5) N3-H3B···O1 iii 0.96 (7) 1.96 (6) 2.909 (8) 169 (6) supplementary materials sup-6