Acetylacetone
- IUPAC: pentane -2 ,4- dione
- Diacetylmethan
- β, δ - Dioxopentan
- 2,4-pentanedione
- Hacac ( as a ligand )
Clear, colorless liquid with a pleasant odor
Liquid
0.98 g · cm -3
-23 ° C.
140 ° C
9 hPa ( 20 ° C)
Slightly soluble in water: 125 g · l-1 (20 ° C)
1.4494 (20 ° C)
Attention
20 ml · m-3 and 83 mg · m-3
- 5000 mg · kg -1 ( LD50, Rabbit, transdermal)
- 1000 mg · kg -1 ( LD50, rat, oral)
Template: Infobox chemical / molecular formula search available
Acetylacetone ( IUPAC name: pentane -2 ,4- dione) is a colorless, sweet-smelling, flammable liquid that is slightly soluble in water. The liquid is very volatile, but are formed at elevated ambient temperature vapors are heavier than air. These vapors may form explosive mixtures with air at temperatures above 34 ° C ( flash point).
Acetylacetone is a precursor of acetyl acetonate (acac), a common bidentate ligand. He also serves as a building block synthesis of heterocyclic compounds, eg drugs such as folic acid synthesis in bacteria -inhibiting sulfamethazine or nicarbazin. Acetylacetone is also used in the manufacture of corrosion inhibitors and rust converters. It is always formed as a companion component, when acetone is used in column chromatography with alumina as the eluent.
Keto -enol tautomerism
The relatively high acid strength can be explained by the outgoing of the two carbonyl groups inductive effect and mesomeric effect (negative charge of the anion about 5- atomiges π - delocalized system ) explain. The arrangement of the carbonyl groups also promotes enolization, since the double bond of the enol is conjugated with the adjacent carbonyl group and the OH group forms a hydrogen bond to the carbonyl group:
Therefore, acetylacetone is present as enol in the liquid state to 80%.
Acetylacetonate
Β -diketone is acetyl acetone as a CH -acidic compound. By deprotonation at the α - carbon is formed from its anion, the acetylacetonate ( acac). Acetylacetone has a pKa value of 8.99 ± 0.06 (25 ° C, I = 0), ie it reacts when mixed with water slightly acidic.
Acetylacetonate is often used as a ligand for transition metals. These are often used as catalyst metal acetylacetonates. In the empirical formula of a complex is abbreviated acac acetylacetonate, such as Rh (CO) 2 acac.
Examples of common metal acetylacetonates are:
- Aluminum (III ) acetylacetonate Al (acac) 3
- Calcium ( II ) acetylacetonate, Ca ( acac) 2
- Chromium (III) acetylacetonate, Cr (acac) 3
- Cobalt (III ) acetylacetonate Co (acac) 3
- Iron (III) - acetylacetonate Fe (acac) 3
- Iridium acetylacetonate Ir (acac) 3
- Copper (I ) acetylacetonate, Cu (acac)
- Copper (II ) acetylacetonate, Cu (acac) 2
- Manganese (III) acetylacetonate, Mn (acac) 3
- Nickel ( II) acetylacetonate, Ni ( acac) 2
- Vanadyl acetylacetonate V ( O) ( acac) 2
- Zinc acetylacetonate Zn ( acac) 2
Properties
The miscibility with water is limited. With increasing temperature the solubility of acetylacetonate in water increases and increases the solubility of water in acetylacetonate.
In aqueous solution, it is not very stable and slowly decomposes by elimination of water to form mesityl oxide.
Safety
The use of the substance formerly used as a flavoring agent has been banned since 2005 within the EU in food, as evidence of genotoxicity exist.