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| Names | |
|---|---|
| Preferred IUPAC name 3-Hydroxybutan-2-one | |
| Other names 3-Hydroxybutanone Acetyl methyl carbinol | |
| Identifiers | |
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3D model (JSmol) | |
| ChEBI |
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| ChemSpider | |
| ECHA InfoCard | 100.007.432 |
| EC Number |
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| KEGG | |
| RTECS number |
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| UNII | |
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| Properties | |
| C4H8O2 | |
| Molar mass | 88.106 g·mol−1 |
| Appearance | colorless liquid |
| Odor | bland, yogurt-like |
| Density | 1.012 g/cm3 |
| Melting point | 15 °C (59 °F; 288 K) |
| Boiling point | 148 °C (298 °F; 421 K) |
| 1000 g/L (20 °C) | |
| Solubility in other solvents | Soluble inalcohol Slightly soluble inether,petroleum ether Miscible inpropylene glycol Insoluble invegetable oil |
| logP | −0.36 |
| Acidity (pKa) | 13.72 |
Chiral rotation ([α]D) | −39.4 |
Refractive index (nD) | 1.4171 |
| Hazards | |
| Flash point | 41 °C (106 °F; 314 K) |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | > 5000 mg/kg (rat, oral) |
| Safety data sheet (SDS) | MSDS |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Acetoin, also known as3-hydroxybutanone oracetyl methyl carbinol, is anorganic compound with the formula CH3CH(OH)C(O)CH3. It is a colorlessliquid with a pleasant, buttery odor. It ischiral. The form produced by bacteria is (R)-acetoin.[1]
Acetoin is a neutral, four-carbon molecule used as an external energy store by a number offermentative bacteria. It is produced by thedecarboxylation of alpha-acetolactate, a common precursor in thebiosynthesis ofbranched-chain amino acids. Owing to its neutral nature, production and excretion of acetoin during exponential growth prevents over-acidification of thecytoplasm and the surrounding medium that would result from accumulation of acidic metabolic products, such asacetic acid andcitric acid. Once superior carbon sources are exhausted, and the culture entersstationary phase, acetoin can be used to maintain the culture density.[2] The conversion of acetoin intoacetyl-CoA is catalysed by theacetoin dehydrogenase complex, following a mechanism largely analogous to thepyruvate dehydrogenase complex; however, as acetoin is not a2-oxoacid, it does not undergo decarboxylation by theE1 enzyme; instead, a molecule ofacetaldehyde is released.[3] In some bacteria, acetoin can also be reduced to2,3-butanediol byacetoin reductase/2,3-butanediol dehydrogenase.
TheVoges–Proskauer test is a commonly used microbiological test for acetoin production.[4]
Acetoin, along withdiacetyl, is one of the compounds that givesbutter its characteristicflavor. Because of this, manufacturers of partiallyhydrogenatedoils typically addartificial butter flavor – acetoin and diacetyl – (along withbeta carotene for the yellow color) to the final product.[5]
Acetoin can be found inapples,yogurt,asparagus,blackcurrants,blackberries,wheat,broccoli,brussels sprouts,cantaloupes, andmaple syrup.[6][7][8]
Acetoin is used as a foodflavoring (inbaked goods) and as afragrance.
It is used inliquids forelectronic cigarettes to give a buttery or caramel flavor.[9]
