Names | |||
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IUPAC names (3Z)-4-Hydroxy-3-penten-2-one (enol form) Pentane-2,4-dione (keto form) | |||
Other names
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Identifiers | |||
3D model (JSmol) | |||
741937 | |||
ChEBI | |||
ChEMBL | |||
ChemSpider | |||
ECHA InfoCard | 100.004.214 | ||
EC Number |
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2537 | |||
KEGG | |||
PubChem CID | |||
RTECS number |
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UNII | |||
UN number | 2310 | ||
CompTox Dashboard (EPA) | |||
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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: | |||
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) | |||
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). |
Acetylacetone is an organic compound with the chemical formula CH3−C(=O)−CH2−C(=O)−CH3. It is classified as a 1,3-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.
Solvent | Kketo→enol |
---|---|
Gas phase | 11.7 |
Cyclohexane | 42 |
Toluene | 10 |
THF | 7.2 |
CDCl3 [3] | 5.7 |
DMSO | 2 |
Water | 0.23 |
The keto and enol tautomers of acetylacetone coexist in solution. The enol form has C2v symmetry, meaning the hydrogen atom is shared equally between the two oxygen atoms. [4] In the gas phase, the equilibrium constant, Kketo→enol, is 11.7, favoring the enol form. The two tautomeric forms can be distinguished by NMR spectroscopy, 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. [7] The enol form is a vinylogous analogue of a carboxylic acid.[ citation needed ]
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 weak acid. It forms the acetylacetonate anion C5H7O−2 (commonly abbreviated acac−):
In the acetylacetonate anion, both C-O bonds are equivalent. Both C-C central bonds are equivalent as well, with one hydrogen atom bonded to the central carbon atom (the C3 atom). Those two equivalencies are because there is a resonance between the four bonds in the O-C2-C3-C4-O linkage in the acetylacetonate anion, where the bond order of those four bonds is about 1.5. Both oxygen atoms equally share the negative charge. The acetylacetonate anion is a bidentate ligand.
IUPAC recommended pKa 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). [9] Values for mixed solvents are available. Very strong bases, such as organolithium compounds, will deprotonate acetylacetone twice. The resulting dilithium species can then be alkylated at the carbon atom at the position 1.
Acetylacetone is prepared industrially by the thermal rearrangement of isopropenyl acetate. [10]
Laboratory routes to acetylacetone also begin with acetone. Acetone and acetic anhydride ((CH3C(O))2O) upon the addition of boron trifluoride (BF3) catalyst: [11]
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]
Because of the ease of these syntheses, many analogues of acetylacetonates are known. Some examples are benzoylacetone, dibenzoylmethane (dbaH)[ clarification needed ] and tert-butyl analogue 2,2,6,6-tetramethyl-3,5-heptanedione. Trifluoroacetylacetone and hexafluoroacetylacetonate are also used to generate volatile metal complexes.
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).
Sodium acetylacetonate, Na(acac), is the precursor to many acetylacetonate complexes. A general method of synthesis is to treat a metal salt with acetylacetone in the presence of a base: [12]
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.
The enzyme acetylacetone dioxygenase cleaves a central carbon-carbon bond of acetylacetone, producing acetate and 2-oxopropanal. The enzyme is iron(II)-dependent, but it has been proven to bind to zinc as well. Acetylacetone degradation has been characterized in the bacterium Acinetobacter johnsonii . [13]
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group attached to an R-group. The general formula of a carboxylic acid is often written as R−COOH or R−CO2H, sometimes as R−C(O)OH with R referring to an organyl group, or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion.
In chemistry, an ester is a compound derived from an acid in which the hydrogen atom (H) of at least one acidic hydroxyl group of that acid is replaced by an organyl group. These compounds contain a distinctive functional group. Analogues derived from oxygen replaced by other chalcogens belong to the ester category as well. According to some authors, organyl derivatives of acidic hydrogen of other acids are esters as well, but not according to the IUPAC.
In organic chemistry, a ketone is an organic compound with the structure R−C(=O)−R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group −C(=O)−. The simplest ketone is acetone, with the formula (CH3)2CO. Many ketones are of great importance in biology and industry. Examples include many sugars (ketoses), many steroids, and the solvent acetone.
Acetoacetic acid is the organic compound with the formula CH3COCH2COOH. It is the simplest beta-keto acid, and like other members of this class, it is unstable. The methyl and ethyl esters, which are quite stable, are produced on a large scale industrially as precursors to dyes. Acetoacetic acid is a weak acid.
In organic chemistry, a dicarbonyl is a molecule containing two carbonyl groups. Although this term could refer to any organic compound containing two carbonyl groups, it is used more specifically to describe molecules in which both carbonyls are in close enough proximity that their reactivity is changed, such as 1,2-, 1,3-, and 1,4-dicarbonyls. Their properties often differ from those of monocarbonyls, and so they are usually considered functional groups of their own. These compounds can have symmetrical or unsymmetrical substituents on each carbonyl, and may also be functionally symmetrical or unsymmetrical.
In organic chemistry, enols are a type of Functional group or intermediate in organic chemistry containing a group with the formula C=C(OH). The term enol is an abbreviation of alkenol, a portmanteau deriving from "-ene"/"alkene" and the "-ol". Many kinds of enols are known.
In chemistry, tautomers are structural isomers of chemical compounds that readily interconvert. The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the relocation of a hydrogen atom within the compound. The phenomenon of tautomerization is called tautomerism, also called desmotropism. Tautomerism is for example relevant to the behavior of amino acids and nucleic acids, two of the fundamental building blocks of life.
Acetone is an organic compound with the formula (CH3)2CO. It is the simplest and smallest ketone. It is a colorless, highly volatile, and flammable liquid with a characteristic pungent odour, very reminiscent of the smell of pear drops.
Meldrum's acid or 2,2-dimethyl-1,3-dioxane-4,6-dione is an organic compound with formula C6H8O4. Its molecule has a heterocyclic core with four carbon and two oxygen atoms; the formula can also be written as [−O−(C 2)−O−(C=O)−(CH2)−(C=O)−].
The organic compound ethyl acetoacetate (EAA) is the ethyl ester of acetoacetic acid. It is a colorless liquid. It is widely used as a chemical intermediate in the production of a wide variety of compounds.
Diacetone alcohol is an organic compound with the formula CH3C(O)CH2C(OH)(CH3)2, sometimes called DAA. This colorless liquid is a common synthetic intermediate used for the preparation of other compounds, and is also used as a solvent.
Hexafluoroacetylacetone is the chemical compound with the nominal formula CF3C(O)CH2C(O)CF3 (often abbreviated as hfacH). This colourless liquid is a ligand precursor and a reagent used in MOCVD. The compound exists exclusively as the enol CF3C(OH)=CHC(O)CF3. For comparison under the same conditions, acetylacetone is 85% enol.
Nickel(II) bis(acetylacetonate) is a coordination complex with the formula [Ni(acac)2]3, where acac is the anion C5H7O−2 derived from deprotonation of acetylacetone. It is a dark green paramagnetic solid that is soluble in organic solvents such as toluene. It reacts with water to give the blue-green diaquo complex Ni(acac)2(H2O)2.
Ruthenium(III) acetylacetonate is a coordination complex with the formula Ru(O2C5H7)3. O2C5H7− is the ligand called acetylacetonate. This compound exists as a dark red solid that is soluble in most organic solvents. It is used as a precursor to other compounds of ruthenium.
Metal acetylacetonates are coordination complexes derived from the acetylacetonate anion (CH
3COCHCOCH−
3) and metal ions, usually transition metals. The bidentate ligand acetylacetonate is often abbreviated acac. Typically both oxygen atoms bind to the metal to form a six-membered chelate ring. The simplest complexes have the formula M(acac)3 and M(acac)2. Mixed-ligand complexes, e.g. VO(acac)2, are also numerous. Variations of acetylacetonate have also been developed with myriad substituents in place of methyl (RCOCHCOR′−). Many such complexes are soluble in organic solvents, in contrast to the related metal halides. Because of these properties, acac complexes are sometimes used as catalyst precursors and reagents. Applications include their use as NMR "shift reagents" and as catalysts for organic synthesis, and precursors to industrial hydroformylation catalysts. C
5H
7O−
2 in some cases also binds to metals through the central carbon atom; this bonding mode is more common for the third-row transition metals such as platinum(II) and iridium(III).
Dibenzoylmethane (DBM) is an organic compound with the formula (C6H5C(O))2CH2. DBM is the name for a 1,3-diketone, but the compound exists primarily as one of two equivalent enol tautomers. DBM is a white solid. Due UV-absorbing properties, derivatives of DBM such as avobenzone, have found applications as sunscreen products.
Phosphatrioxa-adamantane is an organophosphorus compound that is used as a precursor to bulky phosphine ligands. Abbreviated CgPH, it is a white solid.
1,1,1-Trifluoroacetylacetone is the organofluorine compound with the formula CF3C(O)CH2C(O)CH3. It is a colorless liquid. Like other 1,3-diketones, it is used as a precursor to heterocycles, e.g. pyrazoles, and metal chelates. It is prepared by condensation of esters of trifluoroacetic acid with acetone.
Tetraacetylethane is the organic compound with the nominal formula [CH(C(O)CH3)2]2. It is a white solid that has attracted interest as a precursor to heterocycles and metal complexes. It is prepared by oxidation of sodium acetylacetonate:
Sodium acetylacetonate is an organic compound with the nominal formula Na[CH(C(O)CH3)2]. This white, water-soluble solid is the conjugate base of acetylacetone.