(5-Hydroxy-3-methyl-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl)(pyridin-4-yl)methanone monohydrate

In the title compound, C16H15N3O2·H2O, the mean plane of the approximately planar pyrazole ring [maximum deviation = 0.0474 (18) Å] makes dihedral angles of 86.32 (11) and 45.04 (10)° with the phenyl and pyridine rings, respectively. The dihedral angle between the phenyl and pyridine rings is 69.62 (11)°. In the crystal, intermolecular O—H⋯O and O—H⋯N hydrogen bonds connect the components into chains along [010]. The crystal structure is further stabilized by π–π stacking interactions with centroid–centroid distances of 3.7730 (12) Å.

In the title compound, C 16 H 15 N 3 O 2 ÁH 2 O, the mean plane of the approximately planar pyrazole ring [maximum deviation = 0.0474 (18) Å ] makes dihedral angles of 86.32 (11) and 45.04 (10) with the phenyl and pyridine rings, respectively. The dihedral angle between the phenyl and pyridine rings is 69.62 (11) . In the crystal, intermolecular O-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds connect the components into chains along [010]. The crystal structure is further stabilized bystacking interactions with centroid-centroid distances of 3.7730 (12) Å .

Comment
The asymmetric unit of the title compound, Fig. 1, comprises a substituted pyrazole molecule and a solvent water molecule.
The bond lengths (Allen et al., 1987) and angles are within the normal ranges. The dihedral angle the mean plane of the pyrazole ring makes with the phenyl and pyridine rings are 86.32 (11) and 45.04 (10)°, respectively. The dihedral angle between the phenyl ring and the pyridine ring is 69.62 (11)Å.

Experimental
The title compound was synthesized by adding isoniazide (2 mmol) to a solution of benzoylacetone (2 mmol) in ethanol (20 ml). The mixture was refluxed with stirring for half an hour. The resultant solution was filtered and the white single crystals suitable for X-ray structure determination were recrystallized from ethanol by slow evaporation of the solvents at room temperature over several days.

Refinement
The H atoms of the water and hydroxy groups were located in a difference Fourier map and constraied to refine on the parent atom with U iso (H) = 1.5 U eq (O), see Table 1. The remaining H atoms were positioned geometrically with C-H = 0.93-0.97 Å and included in a riding-model approximation with U iso (H) = 1.2 or 1.5 U eq (C). A rotating group model was used for the methyl group.  (5-Hydroxy-3-methyl-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl)(pyridin-4-yl)methanone monohydrate

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 supplementary materials sup-3 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.