Acetylacetonate

Acetylacetone

Names
Preferred IUPAC name Pentane-2,4-dione
Other names Hacac
Identifiers
CAS Number	123-54-6 Y
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:14750 Y
ChemSpider	29001 Y
ECHA InfoCard	100.004.214
KEGG	C15499 Y
UNII	46R950BP4J Y
InChI InChI=1S/C5H8O2/c1-4(6)3-5(2)7/h3H2,1-2H3 Y Key: YRKCREAYFQTBPV-UHFFFAOYSA-N Y InChI=1/C5H8O2/c1-4(6)3-5(2)7/h3H2,1-2H3 Key: YRKCREAYFQTBPV-UHFFFAOYAO
SMILES O=C(C)CC(=O)C CC(=O)CC(=O)C
Properties
Chemical formula	C5H8O2
Molar mass	100.12 g·mol−1
Density	0.975 g/mL
Melting point	−23 °C (−9 °F; 250 K)
Boiling point	140 °C (284 °F; 413 K)
Solubility in water	16 g/100 mL
Magnetic susceptibility (χ)	-54.88·10−6 cm3/mol
Hazards
EU classification (DSD) (outdated)	Harmful (Xn)
R-phrases (outdated)	R10, R22
S-phrases (outdated)	(S2), S21, S23, S24/25
NFPA 704	2 2 0
Flash point	34 °C (93 °F; 307 K)
Autoignition temperature	340 °C (644 °F; 613 K)
Explosive limits	2.4–11.6%
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Acetylacetone is an organic compound that exists in two tautomeric forms that interconvert rapidly and are treated as a single compound in most applications. Although the compound is formally named as the diketone form, pentane-2,4-dione, the enol form forms a substantial component of the material and is actually the favored form in many solvents. 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.

The keto and enol forms of acetylacetone coexist in solution; these forms are tautomers. The enol form has C_2vsymmetry, meaning the hydrogen atom is shared equally between the two oxygen atoms. In the gas phase, the equilibrium constant, K_keto→enol, is 11.7, favoring the enol form. The two tautomeric forms can easily be distinguished by NMR spectroscopy, IR spectroscopy and other methods.

The equilibrium constant tends to remain high in nonpolar solvents; the keto form becomes more favorable in polar, hydrogen-bonding solvents, such as water. The enol form is a vinylogous analogue of a carboxylic acid.

Acetylacetone is a weak acid:

IUPAC recommended pK_a values for this equilibrium in aqueous solution at 25 °C are 8.99 ± 0.04 (I = 0), 8.83 ± 0.02 (I = 0.1 M NaClO₄) and 9.00 ± 0.03 (I = 1.0 M NaClO₄; I = Ionic strength). Values for mixed solvents are available. Very strong bases, such as organolithium compounds, will deprotonate acetylacetone twice. The resulting dilithio species can then be alkylated at C-1.