Acetoin
{{distinguish|Acetone}}
{{chembox
|Verifiedfields = changed
|Watchedfields = changed
|verifiedrevid = 477239174
|ImageFile = Acetoin-2D.svg
|ImageSize = 200px
|ImageName = 3-Hydroxybutanone
|PIN = 3-Hydroxybutan-2-one
|OtherNames = 3-Hydroxybutanone
Acetyl methyl carbinol
|Section1={{Chembox Identifiers
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|ChemSpiderID = 21105851
|ChemSpiderID1 = 388445
|ChemSpiderID1_Comment = (R)
|ChemSpiderID2 = 394765
|ChemSpiderID2_Comment = (S)
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = BG4D34CO2H
|KEGG = C00466
|KEGG1 = C00810
|KEGG1_Comment = (R)
|KEGG2 = C01769
|KEGG2_Comment = (S)
|InChI = 1/C4H8O2/c1-3(5)4(2)6/h3,5H,1-2H3
|InChIKey = ROWKJAVDOGWPAT-UHFFFAOYAD
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChI = 1S/C4H8O2/c1-3(5)4(2)6/h3,5H,1-2H3
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = ROWKJAVDOGWPAT-UHFFFAOYSA-N
|CASNo_Ref = {{cascite|correct|CAS}}
|CASNo = 513-86-0
|CASNo_Comment = (R/S)
|CASNo1_Ref = {{cascite|correct|CAS}}
|CASNo1 = 53584-56-8
|CASNo1_Comment = (R)
|CASNo2_Ref = {{cascite|correct|CAS}}
|CASNo2 = 78183-56-9
|CASNo2_Comment = (S)
|ChEBI_Ref = {{ebicite|correct|EBI}}
|ChEBI = 15688
|ChEBI1 = 15686
|ChEBI1_Comment = (R)
|ChEBI2 = 15687
|ChEBI2_Comment = (S)
|SMILES = CC(=O)C(C)O
|SMILES1 = CC(=O)[C@@H](C)O
|SMILES1_Comment = (R)
|SMILES2 = CC(=O)[C@H](C)O
|SMILES2_Comment = (S)
|PubChem = 179
|PubChem1 = 439314
|PubChem1_Comment = (R)
|PubChem2 = 447765
|PubChem2_Comment = (S)
|EINECS = 208-174-1
|RTECS = EL8790000
}}
|Section2={{Chembox Properties
|C=4 | H=8 | O=2
|Appearance = colorless liquid
|Odor = bland, yogurt-like
|Density = 1.012 g/cm3
|MeltingPtC = 15
|BoilingPtC = 148
|Solubility = 1000 g/L (20 °C)
|SolubleOther = Soluble in alcohol
Slightly soluble in ether, petroleum ether
Miscible in propylene glycol
Insoluble in vegetable oil
|Solvent = other solvents
|LogP = −0.36
|RefractIndex = 1.4171
|SpecRotation = −39.4
|pKa = 13.72
}}
|Section3={{Chembox Hazards
|ExternalSDS = [http://www.thegoodscentscompany.com/msds/md102388.html MSDS]
|FlashPtC = 41
|LD50 = > 5000 mg/kg (rat, oral)
}}
}}
Acetoin, also known as 3-hydroxybutanone or acetyl methyl carbinol, is an organic compound with the formula CH3CH(OH)C(O)CH3. It is a colorless liquid with a pleasant, buttery odor. It is chiral. The form produced by bacteria is (R)-acetoin.Albert Gossauer: Struktur und Reaktivität der Biomoleküle, Verlag Helvetica Chimica Acta, Zürich, 2006, Seite 285, {{ISBN|978-3-906390-29-1}}.
Production in bacteria
Acetoin is a neutral, four-carbon molecule used as an external energy store by a number of fermentative bacteria. It is produced by the decarboxylation of alpha-acetolactate, a common precursor in the biosynthesis of branched-chain amino acids. Owing to its neutral nature, production and excretion of acetoin during exponential growth prevents over-acidification of the cytoplasm and the surrounding medium that would result from accumulation of acidic metabolic products, such as acetic acid and citric acid. Once superior carbon sources are exhausted, and the culture enters stationary phase, acetoin can be used to maintain the culture density.{{cite journal | doi = 10.1080/10408410701364604 |author1=Xiao, Z. |author2=Xu, P. | year = 2007 | title = Acetoin metabolism in bacteria | journal = Crit Rev Microbiol | volume = 33 | issue = 2 | pages = 127–140 | pmid = 17558661|s2cid=46151943 }} The conversion of acetoin into acetyl-CoA is catalysed by the acetoin dehydrogenase complex, following a mechanism largely analogous to the pyruvate dehydrogenase complex; however, as acetoin is not a 2-oxoacid, it does not undergo decarboxylation by the E1 enzyme; instead, a molecule of acetaldehyde is released.{{cite journal |author1=Oppermann, F.B. |author2=Steinbuchel, A. | year = 1994 | title = Identification and molecular characterization of the aco genes encoding the Pelobacter carbinolicus acetoin dehydrogenase enzyme system | journal = J. Bacteriol. | volume = 176 | issue = 2 | pages = 469–485 | pmid = 8110297 | pmc = 205071 | doi=10.1128/jb.176.2.469-485.1994}}
In some bacteria, acetoin can also be reduced to 2,3-butanediol by acetoin reductase/2,3-butanediol dehydrogenase.
The Voges–Proskauer test is a commonly used microbiological test for acetoin production.{{cite journal |author1=Speckman, R.A. |author2=Collins, E.B. | year = 1982 | title = Specificity of the Westerfeld adaptation of the Voges-Proskauer test | journal = Appl Environ Microbiol | volume = 44 | issue = 1 | pages = 40–43 |doi=10.1128/aem.44.1.40-43.1982 | pmid = 6751225 | pmc = 241965|bibcode=1982ApEnM..44...40S }}
Uses
=Food ingredients=
Acetoin, along with diacetyl, is one of the compounds that gives butter its characteristic flavor. Because of this, manufacturers of partially hydrogenated oils typically add artificial butter flavor – acetoin and diacetyl – (along with beta carotene for the yellow color) to the final product.Pavia et al., Introduction to Organic Laboratory Techniques, 4th ed., {{ISBN|978-0-495-28069-9}}
Acetoin can be found in apples, yogurt, asparagus, blackcurrants, blackberries, wheat, broccoli, brussels sprouts, cantaloupes, and maple syrup.{{cite web| url = http://www.aresok.org/npg/nioshdbs/oshamethods/validated/1012/1012.html| url-status = dead| archive-url = https://web.archive.org/web/20180604002419/http://www.aresok.org/npg/nioshdbs/oshamethods/validated/1012/1012.html| archive-date = 2018-06-04| title = Sampling and Analytical Methods: Acetoin, Diacetyl, 1012}}{{Cite web|url=https://allendalecolumbia.org/tag/stem/page/11/|title=Allendale Columbia | STEM}}{{Cite web|url=https://www.fks.com/learningcenter/acetoin.html|title=Evaluation of Natural Acetyl Methyl Carbinol|Flavorist|website=www.fks.com}}
Acetoin is used as a food flavoring (in baked goods) and as a fragrance.
=Electronic cigarettes=
It is used in liquids for electronic cigarettes to give a buttery or caramel flavor.{{cite book |chapter-url=https://www.nap.edu/read/24952/chapter/8?term=Diacetyl#175 |author1=Committee on the Review of the Health Effects of Electronic Nicotine Delivery Systems, National Academies of Sciences|editor1-last=Eaton |editor1-first=David L. |editor2-last=Kwan |editor2-first=Leslie Y. |editor3-last=Stratton |editor3-first=Kathleen |title=Public Health Consequences of E-Cigarettes |date=2018 |publisher=National Academies Press |isbn=9780309468343 |page=175 |language=en |pmid=29894118|chapter=Chapter 5: Toxicology of E-Cigarette Constituents}}