4-Amino-5-methyl-2(1H)-pyridinone
[CAS 95306-64-2]

Identification

• Classification: Organic raw materials >> Ketone compound
• Name: 4-Amino-5-methyl-2(1H)-pyridinone
• Molecular Formula: C₆H₈N₂O
• Molecular Weight: 124.14
• CAS Registry Number: 95306-64-2
• EC Number: 682-818-3
• SMILES: CC1=CNC(=O)C=C1N

Properties

• Solubility: Soluble (70 g/L) (25 °C), Calc.^*
• Density: 1.137±0.06 g/cm³ (20 °C 760 Torr), Calc.^*
• Boiling point: 291.0±33.0 °C (760 Torr), Calc.^*
• Flash point: 129.8±25.4 °C, Calc.^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software V11.02 (©1994-2013 ACD/Labs)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H315-H319-H335
• Safety Statements: P261-P305+P351+P338

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	3	H301
Acute toxicity	Acute Tox.	4	H302

Discovery and Applications

4-Amino-5-methyl-2(1H)-pyridinone is a small heterocyclic organic compound derived from a substituted pyridone framework. It belongs to the class of aminopyridinones, which contain both an amino group and a lactam (pyridone) functionality on a six-membered nitrogen-containing aromatic system.

Structurally, the molecule is based on a pyridinone ring, which is a partially aromatic heterocycle containing one nitrogen atom in the ring and a carbonyl group at the 2-position. In the 2(1H)-pyridinone tautomeric form, the structure is best described as a cyclic amide (lactam), where the carbonyl group is conjugated with the adjacent C=C bonds of the heterocycle. This conjugation contributes to partial aromatic stabilization and influences the electron distribution across the ring.

At the 4-position, the compound carries an amino substituent (–NH2). This group is strongly electron-donating through resonance, allowing the nitrogen lone pair to interact with the π-system of the heterocycle. This increases electron density in the ring and can significantly influence hydrogen bonding behavior and chemical reactivity.

At the 5-position, there is a methyl substituent. This group contributes electron density through inductive effects and increases hydrophobic character. It also introduces mild steric influence, which can affect the overall shape and intermolecular interactions of the molecule.

The 2(1H)-pyridinone system exhibits tautomerism between the lactam form (2-pyridinone) and the lactim form (2-hydroxypyridine). In this equilibrium, the proton can shift between nitrogen and oxygen, altering the distribution of double bonds. The lactam form is generally more stable under standard conditions due to the strength of the carbonyl bond.

The ring system is largely planar due to conjugation between the carbonyl group, the nitrogen atom, and the adjacent double bonds. This planarity allows for delocalization of electrons and contributes to resonance stabilization of both the neutral and protonated forms.

From a physicochemical perspective, 4-amino-5-methyl-2(1H)-pyridinone is moderately polar. The carbonyl group provides a strong hydrogen bond acceptor site, while the amino group can act as both a hydrogen bond donor and acceptor depending on its protonation state. This enables extensive intermolecular hydrogen bonding in solid-state and solution environments.

The compound is amphiphilic to a limited extent: the heterocyclic core and carbonyl group are polar, while the methyl substituent adds hydrophobic character. Overall, polarity dominates due to the presence of multiple heteroatoms.

Chemically, the most reactive sites include the amino group and the carbonyl functionality. The amino group can undergo protonation, acylation, or diazotization under suitable conditions, while the carbonyl group can participate in nucleophilic addition or tautomeric exchange. The electron-rich ring system may also undergo electrophilic substitution, although the presence of the carbonyl group generally deactivates the ring toward such reactions.

The compound’s electronic structure is influenced by the interplay between electron-donating (amino) and electron-withdrawing (carbonyl) groups, resulting in a polarized heteroaromatic system. This internal electronic balance affects its reactivity profile and hydrogen bonding network.

Overall, 4-amino-5-methyl-2(1H)-pyridinone is a substituted pyridinone heterocycle featuring a lactam carbonyl, an electron-donating amino group, and a methyl substituent. Its conjugated ring system, tautomeric behavior, and hydrogen bonding capacity define its chemical properties and make it a representative example of functionalized aminopyridinones.

References

2022. Finerenone. Pharmaceutical Substances.
URL: https://pharmaceutical-substances.thieme.com/ps/search-results?docUri=KD-06-0143