Title: Acetylacetone
CAS Registry Number: 123-54-6
CAS Name: 2,4-Pentanedione
Additional Names: diacetylmethane
Molecular Formula: C5H8O2
Molecular Weight: 100.12
Percent Composition: C 59.98%, H 8.05%, O 31.96%
Line Formula: CH3COCH2COCH3
Literature References: Made by the action of sodium on ethyl acetate and acetone or by the action of anhydrous aluminum chloride on acetyl chloride in the presence of an inert solvent: Combes, Compt. Rend. 103, 814 (1886); Ann. Chim. (Paris) 12, 199 (1887); Claisen, Ber. 38, 695 (1905); Hunt, US 2737528 (1956 to Shawinigan Chem.); Georgieff, US 2834811 (1958); Gattermann-Wieland, Praxis des Organischen Chemikers (de Gruyter, Berlin, 40th ed, 1961) p 219. Toxicity data: Carpenter, J. Ind. Hyg. Toxicol. 31, 343 (1949).
Properties: Colorless or slightly yellow, flammable liquid; pleasant odor. d 0.976. bp 140.5°. mp -23°. nD20 1.4512. One part dissolves in about 8 parts of water. Miscible with alcohol, benzene, chloroform, ether, acetone, glacial acetic acid. LC50 (4 hrs) in rats: 1000 ppm (Carpenter).
Melting point: mp -23°
Boiling point: bp 140.5°
Index of refraction: nD20 1.4512
Density: d 0.976
Toxicity data: LC50 (4 hrs) in rats: 1000 ppm (Carpenter)
CAUTION: Mild irritant to skin, mucous membranes.
Use: Forms organometallic complexes which are used as gasoline additives, lubricant additives, driers for varnishes and printer's inks, fungicides, insecticides, colors.
Acetylcarnitine Acetylcholine Bromide Acetylcholine Chloride Acetyldigitoxins Acetylene

acac redirects here. For other uses, see ACAC.
Skeletal structures of both tautomers
Ball-and-stick model of the enol tautomer Ball-and-stick model of the keto tautomer
CAS number 123-54-6 YesY
ChemSpider 29001 YesY
UNII 46R950BP4J YesY
KEGG C15499 YesY
ChEBI CHEBI:14750 YesY
Jmol-3D images Image 1
Image 2
Molecular formula C5H8O2
Molar mass 100.12 g mol−1
Density 0.975 g/mL[1]
Melting point −23 °C; −9 °F; 250 K
Boiling point 140 °C; 284 °F; 413 K
Solubility in water 16 g/100 mL
EU Index 606-029-00-0
EU classification Harmful (Xn)
R-phrases R10, R22
S-phrases (S2), S21, S23, S24/25
NFPA 704
NFPA 704.svg
Flash point 34 °C; 93 °F; 307 K
Autoignition temperature 340 °C; 644 °F; 613 K
Explosive limits 2.4–11.6%
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Acetylacetone is an organic compound that famously exists in two tautomeric forms that rapidly interconvert. The more stable tautomer is a diketone[2] formally named pentane-2,4-dione. The less common tautomer is the enol form. The pair of tautomers rapidly interconvert and are treated as a single compound in most applications. It is a colourless liquid that is a precursor to acetylacetonate (acac), a common bidentate ligand. It is also a building block for the synthesis of heterocyclic compounds.