Biacetyl

Diacetyl
Names


Preferred IUPAC name Butane-2,3-dione
Other names Diacetyl Biacetyl Dimethyl diketone 2,3-Diketobutane
Identifiers
CAS Number	431-03-8^Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:16583^Y
ChemSpider	630^Y
ECHA InfoCard	100.006.428
KEGG	C00741^Y
PubChem CID	650
UNII	K324J5K4HM^Y
InChI InChI=1S/C4H6O2/c1-3(5)4(2)6/h1-2H3^Y Key: QSJXEFYPDANLFS-UHFFFAOYSA-N^Y InChI=1/C4H6O2/c1-3(5)4(2)6/h1-2H3 Key: QSJXEFYPDANLFS-UHFFFAOYAX
SMILES CC(=O)C(=O)C
Properties
Chemical formula	C₄H₆O₂
Molar mass	86.09 g·mol⁻¹
Appearance	Yellowish green liquid
Density	0.990 g/mL at 15 °C
Melting point	−2 to −4 °C (28 to 25 °F; 271 to 269 K)
Boiling point	88 °C (190 °F; 361 K)
Solubility in water	200 g/L (20 °C)
Hazards
Main hazards	Harmful, flammable
Safety data sheet	External MSDS
R-phrases	R10 R22 R36 R37 R38
S-phrases	S9 S16 S33
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y (what is ^YN ?)
Infobox references

Diacetyl (IUPAC systematic name: butanedione or butane-2,3-dione) is an organic compound with the chemical formula (CH₃CO)₂. It is a yellow/green liquid with an intensely buttery flavor. It is a vicinal diketone (two C=O groups, side-by-side) with the molecular formula C₄H₆O₂. Diacetyl occurs naturally in alcoholic beverages and is added to some foods to impart its buttery flavor.

A distinctive feature of diacetyl (and other 1,2-diketones) is the long C–C bond linking the carbonyl centers. This bond distance is about 1.54 Å, compared to 1.45 Å for the corresponding C–C bond in 1,3-butadiene. The elongation is attributed to repulsion between the polarized carbonyl carbon centers.

Diacetyl arises naturally as a byproduct of fermentation. In some fermentative bacteria, it is formed via the thiamine pyrophosphate-mediated condensation of pyruvate and acetyl CoA. Sour (cultured) cream, cultured buttermilk, and cultured butter are produced by inoculating pasteurized cream or milk with a lactic starter culture, churning (agitating) and holding the milk until a desired pH drop (or increase in acidity) is attained. Cultured cream, cultured butter, and cultured buttermilk owe their tart flavour to lactic acid bacteria and their buttery aroma and taste to diacetyl.

Diacetyl is produced industrially by dehydrogenation of 2,3-butanediol. Acetoin is an intermediate.

Diacetyl and acetoin are two compounds that give butter its characteristic taste. Because of this, manufacturers of artificial butter flavoring, margarines or similar oil-based products typically add diacetyl and acetoin (along with beta-carotene for the yellow color) to make the final product butter-flavored, because it would otherwise be relatively tasteless.

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Wikipedia