Acetylacetone (2,4-Pentanedione): Structure, Properties, and Applications

Acetylacetone, also known as 2,4-Pentanedione, is an organic compound with the chemical formula C₅H₈O₂. It is a key reagent in coordination chemistry, organic synthesis, and industrial applications. Acetylacetone exists in equilibrium between its keto and enol forms, making it a versatile compound in various chemical reactions.

Chemical Structure and Formula

• Molecular Formula: C₅H₈O₂
• IUPAC Name: 2,4-Pentanedione
• Structure: CH₃-CO-CH₂-CO-CH₃
• Molecular Weight: 100.12 g/mol
• Functional Groups: Keto and enol groups

Tautomerism: Keto-Enol Equilibrium

Acetylacetone exists in two tautomeric forms:

1. Keto Form: CH₃-CO-CH₂-CO-CH₃ (dominates in non-polar solvents)
2. Enol Form: CH₃-C(OH)=CH-CO-CH₃ (stabilized by intramolecular hydrogen bonding)

In solution, a dynamic equilibrium exists between these forms, with the enol form being more stable due to hydrogen bonding.

Physical Properties : Acetylacetone

• Appearance: Colorless to pale yellow liquid
• Odor: Mild, characteristic odor
• Boiling Point: ~140°C
• Density: 0.975 g/cm³
• Solubility: Miscible with water, ethanol, and most organic solvents

Chemical Properties : Acetylacetone

1. Acidic Nature:
   • The enol form has an acidic hydrogen, allowing acetylacetone to act as a weak acid.
2. Chelation Ability:
   • Forms stable metal chelates with transition metals like Fe³⁺, Co²⁺, and Cu²⁺.
3. Reactivity in Organic Synthesis:
   • Can undergo condensation reactions to form heterocycles.
   • Used in Michael additions and aldol condensations.

Applications of Acetylacetone

1. Metal Chelation:
   • Used to synthesize metal-acetylacetonate complexes in catalysis and material science.
2. Solvent and Intermediate:
   • Used as a solvent and precursor in pharmaceuticals, agrochemicals, and coatings.
3. Organic Synthesis:
   • Used in the synthesis of heterocyclic compounds and bioactive molecules.
4. Analytical Chemistry:
   • Forms colored complexes for spectroscopic analysis of metal ions.

Safety and Handling : 2,4-Pentanedione

• Flammability: Highly flammable, handle with care.
• Toxicity: Can cause skin and eye irritation; should be handled with gloves and goggles.
• Storage: Store in a cool, dry place away from heat sources.

Conclusion

Acetylacetone is a versatile organic compound with significant applications in coordination chemistry, industrial manufacturing, and organic synthesis. Its unique tautomeric behavior and metal-chelating properties make it an essential reagent in scientific research and industrial processes.

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