Acetylacetone

Source: Wikipedia, the free encyclopedia.
"Acac" redirects here. For other uses, see ACAC (disambiguation).
Acetylacetone
Skeletal structures of both tautomers
Ball-and-stick model of the enol tautomer
Ball-and-stick model of the enol tautomer
Ball-and-stick model of the keto tautomer
Ball-and-stick model of the keto tautomer
Space-filling model of the enol tautomer
Space-filling model of the enol tautomer
Space-filling model of the keto tautomer
Space-filling model of the keto tautomer
Names
IUPAC names
(3Z)-4-Hydroxy-3-penten-2-one (enol form)
Pentane-2,4-dione (keto form)
Other names
  • Hacac
  • 2,4-Pentanedione
Identifiers
3D model (
JSmol
)
741937
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard
 100.004.214 Edit this at Wikidata
EC Number
  • 204-634-0
2537
KEGG
RTECS number
  • SA1925000
UNII
UN number 2310
  • InChI=1S/C5H8O2/c1-4(6)3-5(2)7/h3H2,1-2H3 checkY
    Key: YRKCREAYFQTBPV-UHFFFAOYSA-N checkY
  • InChI=1/C5H8O2/c1-4(6)3-5(2)7/h3H2,1-2H3
    Key: YRKCREAYFQTBPV-UHFFFAOYAO
  • O=C(C)CC(=O)C
  • CC(=O)CC(=O)C
  • Enol form: CC(O)=CC(=O)C
Properties
C5H8O2
Molar mass 100.117 g·mol−1
Appearance Colorless liquid
Density 0.975 g/mL[1]
Melting point −23 °C (−9 °F; 250 K)
Boiling point 140 °C (284 °F; 413 K)
16 g/(100 mL)
−54.88·10−6 cm3/mol
Hazards
GHS labelling:
GHS02: FlammableGHS06: ToxicGHS07: Exclamation markGHS08: Health hazard
Danger
H226, H302, H311, H320, H331, H335, H341, H370, H412
P201, P202, P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P273, P280, P281, P301+P312, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P307+P311, P308+P313, P311, P312, P321, P322, P330, P337+P313, P361, P363, P370+P378, P403+P233, P403+P235, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
2
0
Flash point 34 °C (93 °F; 307 K)
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).
checkY verify (what is checkY☒N ?)

Acetylacetone is an

diketone. It exists in equilibrium with a tautomer CH3−C(=O)−CH=C(−OH)−CH3. The mixture is a colorless liquid. These tautomers interconvert so rapidly under most conditions that they are treated as a single compound in most applications.[2] Acetylacetone is a building block for the synthesis of many coordination complexes as well as heterocyclic compounds
.

Properties

Tautomerism

Solvent Kketo→enol
Gas phase 11.7
Cyclohexane 42
Toluene 10
THF
 7.2
CDCl3[3] 5.7
DMSO
 2
Water 0.23

The

IR spectroscopy and other methods.[5][6]

The equilibrium constant tends to be high in nonpolar solvents; when Kketo→enol is equal or greater than 1, the enol form is favoured. The keto form becomes more favourable in polar, hydrogen-bonding solvents, such as water.

vinylogous analogue of a carboxylic acid
.

Acid–base properties

Solvent T/°C pKa[8]
40% ethanol/water 30 9.8
70%
dioxane
/water		 28 12.5
80%
DMSO
/water		 25 10.16
DMSO 25 13.41

Acetylacetone is a

anion
C5H7O−2 (commonly abbreviated acac−):

C5H8O2 ⇌ C5H7O−2 + H+
The structure of the acetylacetonate anion (acac−)

In the acetylacetonate anion, both

bidentate ligand
.

alkylated at the carbon atom at the position 1
.

Preparation

Acetylacetone is prepared industrially by the thermal rearrangement of isopropenyl acetate.[10]

Synthese von Acetylaceton

Laboratory routes to acetylacetone also begin with acetone. Acetone and acetic anhydride ((CH3C(O))2O) upon the addition of boron trifluoride (BF3) catalyst:[11]

(CH3C(O))2O + CH3C(O)CH3 → CH3C(O)CH2C(O)CH3

A second synthesis involves the base-catalyzed condensation (e.g., by sodium ethoxide CH3CH2O−Na+) of acetone and ethyl acetate, followed by acidification of the sodium acetylacetonate (e.g., by hydrogen chloride HCl):[11]

CH3CH2O−Na+ + CH3C(O)OCH2CH3 + CH3C(O)CH3 → Na+[CH3C(O)CHC(O−)CH3] + 2 CH3CH2OH
Na+[CH3C(O)CHC(O−)CH3] + HCl → CH3C(O)CH2C(O)CH3 + NaCl

Because of the ease of these syntheses, many analogues of acetylacetonates are known. Some examples are

metal complexes
.

Reactions

Condensations

Acetylacetone is a versatile bifunctional precursor to heterocycles because both keto groups may undergo condensation. For example, condensation with Hydrazine produces pyrazoles while condensation with Urea provides pyrimidines. Condensation with two aryl- or alkylamines gives NacNacs, wherein the oxygen atoms in acetylacetone are replaced by NR (R = aryl, alkyl).

Coordination chemistry

Main article: Metal acetylacetonates
A ball-and-stick model of VO(acac)2

acetylacetonate complexes. A general method of synthesis is to treat a metal salt with acetylacetone in the presence of a base:[12]

MBz + z Hacac ⇌ M(acac)z + z BH

Both oxygen atoms bind to the metal to form a six-membered chelate ring. In some cases the

chelate effect
is so strong that no added base is needed to form the complex.

Biodegradation

The enzyme

Acinetobacter johnsonii.[13]

C5H8O2 + O2 → C2H4O2 + C3H4O2

References

  1. ^ "05581: Acetylacetone". Sigma-Aldrich.
  2. ISBN 0471936235
    .
  3. doi:10.1021/acs.jchemed.5b00170
    .
  4. PMID 16417375
    .
  5. doi:10.1021/ed1010932
    .
  6. doi:10.1016/0040-4020(70)80005-9
    .
  7. ISBN 3-527-30618-8
    .
  8. ^ IUPAC SC-Database Archived 2017-06-19 at the Wayback Machine A comprehensive database of published data on equilibrium constants of metal complexes and ligands
  9. S2CID 96848983
    .
  10. ISBN 9783527306732
    .
  11. ^
    doi:10.15227/orgsyn.020.0006
    .
  12. ^ O'Brien, Brian. "Co(tfa)3 & Co(acac)3 handout" (PDF). Gustavus Adolphus College.
  13. PMID 12379146
    .

External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Acetylacetone&oldid=1215877202"