I hope my short article helps more people learn about this compound(5-Hydroxynicotinic acid)Recommanded Product: 5-Hydroxynicotinic acid. Apart from the compound(27828-71-3), you can read my other articles to know other related compounds.
Recommanded Product: 5-Hydroxynicotinic acid. The protonation of heteroatoms in aromatic heterocycles can be divided into two categories: lone pairs of electrons are in the aromatic ring conjugated system; and lone pairs of electrons do not participate. Compound: 5-Hydroxynicotinic acid, is researched, Molecular C6H5NO3, CAS is 27828-71-3, about Energetics and Structure of Hydroxynicotinic Acids. Crystal Structures of 2-, 4-, 6-Hydroxynicotinic and 5-Chloro-6-hydroxynicotinic Acids. Author is Santos, Rui C.; Figueira, Rita M. B. B. M.; Piedade, M. Fatima M.; Diogo, Herminio P.; Minas da Piedade, Manuel E..
The relationship between energetics and structure in 2-, 4-, 5-, and 6-hydroxynicotinic and 5-chloro-6-hydroxynicotinic acids (2HNA, 4HNA, 5HNA, 6HNA, and 5Cl6HNA, resp.) was investigated in the solid and gaseous phases by means of a variety of exptl. and computational chem. techniques. The mol. and crystal structures of the 2HNA, 4HNA, 6HNA, and 5Cl6HNA solid forms used in this study were determined by single crystal X-ray diffraction at 293 ± 2 K. The 2HNA, 4HNA, and 5Cl6HNA samples were monoclinic (space groups: P21/n for 2HNA and P21/c for 4HNA and 5Cl6HNA), and that of 6HNA was found to be triclinic (space group: P1)̅. The 2HNA sample investigated corresponds to a new polymorphic form of this compound The 2HNA, 4HNA, 6HNA, and 5Cl6HNA mols. crystallize as oxo tautomers exhibiting N-H and Cring=O bonds. This is also supported by the observation of bands typical of N-H and Cring=O stretching frequencies in the corresponding FT-IR spectra. The absence of these bands in the spectrum of 5HNA indicates that a hydroxy tautomer with an unprotonated N heteroatom and a Cring-OH bond is likely to be present in this case. Results of theor. calculations carried out at the G3MP2 and CBS-QB3 levels of theory suggest that in the ideal gas phase, at 298.15 K, 2HNA favors the oxo form, 4HNA prefers the hydroxy form, and no strong dominance of one of the two tautomers exists in the case of 6HNA and 5Cl6HNA. The standard molar enthalpies of formation of 2HNA, 4HNA, 5HNA, 6HNA, and 5Cl6HNA in the crystalline state, at 298.15 K, ΔfHmo(cr), were determined by micro combustion calorimetry. The corresponding enthalpies of sublimation, ΔsubHmo, were also derived from vapor pressure vs. temperature measurements by the Knudsen effusion method. The obtained ΔfHmo(cr) and ΔsubHmo values led to the enthalpies of formation of 2HNA, 4HNA, 5HNA, 6HNA, and 5Cl6HNA in the gaseous phase. These were discussed together with the corresponding predictions by the B3LYP/cc-pVTZ, B3LYP/aug-cc-pVTZ, G3MP2, and CBS-QB3 methods on the basis of isodesmic or atomization reactions. The exptl. “”stability”” order (more stable meaning a more neg. ΔfHmo(g) value) found was 5Cl6HNA > 2HNA > 6HNA > 4HNA > 5HNA, and it was accurately captured by the CBS-QB3 and G3MP2 methods, which give 5Cl6HNA > 2HNA ∼ 6HNA > 4HNA > 5HNA, irresp. of the use of isodesmic or atomization reactions. In contrast, only when well-balanced isodesmic reactions were considered did the DFT results agree with the exptl. ones. The picture that emerged from the structural and energetic studies carried out in this work was also discussed in light of that typical of hydroxypyridines, which are generally regarded as the archetype systems for the study of the hydroxy ↔ oxo tautomerization in N-heterocyclic compounds
I hope my short article helps more people learn about this compound(5-Hydroxynicotinic acid)Recommanded Product: 5-Hydroxynicotinic acid. Apart from the compound(27828-71-3), you can read my other articles to know other related compounds.
Reference:
Chapter 1 An introduction to palladium catalysis,
Palladium/carbon catalyst regeneration and mechanical application method