Pyridone may refer to several organic compounds with the formula :
*
2-Pyridone
2-Pyridone is an organic compound with the formula . It is a colourless solid. It is well known to form hydrogen bonded dimers and it is also a classic case of a compound that exists as tautomers.
Tautomerism
The second tautomer is 2-hydroxy ...
*3-hydroxypyridine
*
4-Pyridone
4-Pyridone is an organic compound with the formula . It is a colorless solid.
Preparation
4-Pyridone, and its derivatives, are prepared from 4-pyrone and amines in protic solvents.
:
Tautomerism
4-Pyridone exists a keto-enol tautomerism with ...
These can adopt three
tautomers
In chemistry, tautomers () are structural isomers (constitutional isomers) of chemical compounds that readily interconvert.
The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the reloca ...
, a oxo form, a
zwitterion
In chemistry, a zwitterion ( ; ), also called an inner salt or dipolar ion, is a molecule that contains an equal number of positively and negatively charged functional groups.
:
(1,2- dipolar compounds, such as ylides, are sometimes excluded from ...
form, and a enol form. Whereas 2-pyridone (α) and 4-pyridone (γ) predominantly adopt the oxo form, the 3-pyridone (β) cannot, and instead adopts an equilibrium of the
zwitterion
In chemistry, a zwitterion ( ; ), also called an inner salt or dipolar ion, is a molecule that contains an equal number of positively and negatively charged functional groups.
:
(1,2- dipolar compounds, such as ylides, are sometimes excluded from ...
form, pyridin-1-ium-3-olate, and the enol form, 3-hydroxypyridine (the canonical form). The 3-pyridone is not
mesoionic
In chemistry, mesoionic compounds are one in which a heterocyclic structure is dipolar and where both the negative and the positive charges are delocalized. A completely uncharged structure cannot be written and mesoionic compounds cannot be repr ...
. This property of 3-hydroxypyridine is leveraged in biology in
pyridoxal phosphate
Pyridoxal phosphate (PLP, pyridoxal 5'-phosphate, P5P), the active form of vitamin B6, is a coenzyme in a variety of enzymatic reactions. The International Union of Biochemistry and Molecular Biology has catalogued more than 140 PLP-dependen ...
: this common cofactor that catalyses a variety of reactions thanks to a stable cationic form.
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