1-(4-Fluorophenyl)-2-(1H-1,2,4-triazol-1-yl)ethanone hemihydrate

In the title compound, C10H8FN3O·0.5H2O, the dihedral angle between the mean planes of the rings is 99.80 (4)°. The water molecule lies on a twofold axis. Weak intermolecular O—H⋯N and C—H⋯O hydrogen bonds link one water molecule with four phenylethanone molecules, while intermolecular C—H⋯O hydrogen bonds involving the ketone group link phenylethanone molecules into layers parallel to (100).

In the title compound, C 10 H 8 FN 3 OÁ0.5H 2 O, the dihedral angle between the mean planes of the rings is 99.80 (4) . The water molecule lies on a twofold axis. Weak intermolecular O-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonds link one water molecule with four phenylethanone molecules, while intermolecular C-HÁ Á ÁO hydrogen bonds involving the ketone group link phenylethanone molecules into layers parallel to (100).
Experimental Crystal data

Structure Reports Online
The molecular structure of the title compound is reported in Fig. 1. The bond lengths (Allen et al., 1987) and angles are within normal ranges. The dihedral angle between the mean planes of the N1/N2/C9-C11 and C1-C6 rings is 99.80 (4)°. The solvent molecules of water lie on two-fold axes. The second position of the hydrogen atom is reproduced by the symmetry operation (-x, y, 0.5-z). Weak intermolecular O-H···N ( Fig. 2) and C-H···O hydrogen bonds link one isolated water molecule with four phenylethanone molecules while intermolecular C-H···O hydrogen bonds involving the ketone group link phenylethanone molecules together into layers parallel to (100).
Recrystallization with ethanol yielded a white deposit (m.p. 397-400 K). Crystals suitable for a X-ray analysis study were obtained by dissolving the crude product (1.0 g) in 95% ethanol (30 ml) and then allowing the solution to evaporate slowly at room temperature for about 7 days.

Refinement
The water H atom (the second position being obtained by a symmetry operation) was located in a Fourier difference map and freely refined with U iso (H) = 1.2U eq (O). The other H atoms were positioned geometrically with C-H = 0.93 Å (aromatic) and 0.97 Å (methylene) and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C).