Two Polymorphic Forms of 3-Hydroxy-2-methyl-4H-pyran-4-one (Maltol)

The crystal structures of two polymorphic forms of maltol, C₆H₆O₃, have been determined. The polymorphs exhibit different crystal-packing arrangements through intermolecular hydrogen bonding involving the hydroxyl H atoms. Form (1) has a near planar chain of molecules linked by hydrogen bonds while form (2) has mutually hydrogen-bonded dimers. In both polymorphic forms, there are also weaker C-H...O bonds which give greater stability to the chains of form (1) and link the dimers in form (2).

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