5-Hydroxy-2-methyl-4H-pyran-4-one

The title compound, C6H6O3, is a member of the pyrone family. The molecules are planar (r.m.s. deviation of the asymmetric unit is 0.0248 Å, whereas that of the dimer is 0.0360 Å) and they are dimerized due to intermolecular O—H⋯O hydrogen bonds. The dimers are connected to each other through hydrogen bonds involving the CH3 group and the hydroxy O atom. There are π–π interactions between the centroids of the pyrone rings at a distance of 3.8552 (13) Å. A C—H⋯π interaction also exists between the carbonyl group and the centroid CgA of the pyrone ring, with O⋯CgA = 3.65 (1) Å and C⋯CgA = 4.363 (2) Å.


Structure Reports Online
The crystal structures of 3-Hydroxy-4-pyrone (Tak et al., 1994) has been published which have same heterocyclic ring as of title compound. 3-Hydroxy-2-methyl-4H-pyran-4-one (Rahman et al., 1997) has also been published which is chemical isomer of (I) but have different position of CH 3 . The title compound has been prepared for various purposes such as complexation and as an intermediate ligand.
The heterocyclic ring is not regular as it has two C-C [1.426 (3) (Fig. 2). The dimers are linked to each other through H-bond between CH 3 and hydroxy groups. The molecules may be stabilized due to π-π interaction between the centroids of the ring A (O1/C1-C5). The distance between the centroids of CgA and CgA i [Symmetry code: i = -x, 1 -y, 1 -z] is 3.8552 (13) Å. There exist a C3═O3···π interaction (Table 1), as well.

Experimental
A mixture of 2-chloromethyl-5-hydroxy-4-pyron (1.0 g, 0.6 mmol) and zinc dust (0.8 g, 12 mmol) in water (20 ml) was stirred for 30 min at 323 K. Concentrated HCl (6 ml) was added dropwise to dissolve the zinc dust completely and the mixture was stirred for 3 h at 353 K. The reaction mixture was transferred to ice-water and extracted with dichloromethane, dried with anhydrous Na 2 SO 4 and evaporated to dryness. The crystals of the title compound were obtained by recrystallizing the crude product in isopropanol.

Refinement
The coordinates of H atom of hydroxy group were refined. H atoms were positioned geometrically, with C-H = 0.93 and 0.96 Å for aromatic and methyl H, and constrained to ride on their parent atoms, with U iso (H) = xU eq (C, O), where x = 1.5 for methyl H, and x = 1.2 for other H atoms.
supplementary materials sup-2 Figures   Fig. 1. ORTEP drawing of the title compound, with the atom numbering scheme. The thermal ellipsoids are drawn at the 30% probability level. H atoms are shown by small circles of arbitrary radii.