| Abstract: | Two polymorphs of the title compound, C5H5NO, (I), have been obtained from ethanol. One polymorph crystallizes in the monoclinic space group C2/c [henceforth (I)‐M], while the other crystallizes in the orthorhombic space group Pbca [henceforth (I)‐O]. In the two forms, the lattice parameters, cell volume and packing motifs are very similar. There are also two independent molecules of 4‐pyridone in each asymmetric unit. The molecules are linked by N—H...O hydrogen bonds into one‐dimensional zigzag chains extending along the b axis in the (I)‐M polymorph and along the a axis in the (I)‐O polymorph, with the graph set C22(12). The structures are stabilized by weak C—H...O hydrogen bonds linking adjacent chains, thus forming a ring with the graph set R65(28). The significance of this study lies in the analysis of the hydrogen‐bond interactions occurring in these structures. Analyses of the crystal structures of the two polymorphs of 4‐pyridone are helpful in elucidating the mechanism of the generation of spectroscopic effects observed in the IR spectra of these polymorphs in the frequency range of the N—H stretching vibration band. |
