2-Pyridone, C₅H₅NO, crystal structure refinements at 295 Κ and 120 Κ, experimental and theoretical deformation density studies

Abstract

2-Pyridone, C 5 H 5 NO, has been studied by single crystal diffraction at 295 Κ and 120 Κ using X-ray and neutron diffraction methods. The crystal structure of this compound was first studied by Penfold [Acta Crystallogr. 6, 591 -600 (1953)] but described in an unusual setting. We confirmed this structure at both temperatures and refined the structure in the usual setting. Deformation density studies based on the 120 Κ data were performed using the multipole and charge cloud models. They are compared with the theoretical (4 -31G + BF) dynamic deformation density.

Electron-Induced Phase Transition in Hydrogen-Bonded Solid-State 2-Pyridone

“…The X-ray structure determination of the stable (β) form of 2-pyridone by Penfold, in the early 1950s identified the tautomeric form of the compound not as 2-hydroxypyridine, but as 2-pyridone, with protons bonded to nitrogen atoms . The structure was redetermined recently using modern methods. , The proton positions were also confirmed in our studies. Hence it is absolutely certain that the hydrogen positions in the hydrogen bonds have been fully proved.…”

“…The results of our spectroscopic studies have proved that in the case of cyclic dimers in the α phase of 2-pyridone a single hydrogen bond is considerably stronger than a single hydrogen bond in a chain of molecules in the β phase. This fact suggests that the N + −H···O − bonds exist only in the α phase and that these bonds are obviously stronger than the N−H···O hydrogen bonds in the β phase, since ionic hydrogen bonds are generally known to be stronger than the neutral ones. ,,, This corresponds with the structural data characterizing the geometry of hydrogen bonds in the two different polymorphs: In the α phase the hydrogen bonds are shorter when compared with the hydrogen bond lengths in the β phase. − , …”

“…Crystals of the commercial 2-pyridone are orthorhombic, space group P 2 1 2 1 2 1 , a = 13.585(2) Å, b = 5.806(3) Å, c = 5.603(2) Å, Z = 4. The associated molecules form twisting open molecular chains linked via the N−H···O hydrogen bonds − that elongate along the “ c ” axis. The only nonconventional C−H···O interactions (H···O 2.57 Å) are presumably weak.…”

“…In this paper, results of experimental and theoretical studies are presented for 2-pyridone crystals. − For many years the problem of tautomerism of 2-pyridone dimers has been intensively investigated using advanced experimental and theoretical methods. − This molecular system is also particularly interesting since by chance we managed to identify a phase transition in the solid state. In this case the phase transition is responsible for some spectacular but quite puzzling spectral changes in the frequency ranges of the proton and deuteron stretching vibrations in the hydrogen and deuterium bonds of the crystal.…”

Influence of Excipients on Cocrystal Stability and Formation

“…The structure of the ctz-hyp cocrystal is not known. However, 2-hydroxypyridine predominantly exists as the 2-pyridone tautomer in the solid state 44,45 and may therefore also lack the NHsulfonamide ... Npy motif. Bza and cbz cocrystallise with ctz during milling with added PVP.…”