Diacetyl

CAS 431-03-8

Diacetyl is the compound that smells of butter. It forms naturally in butter, cultured cream and beer, and is added as a flavouring — most famously to butter-flavoured popcorn.

Where it is and isn’t permitted

Status of Diacetyl by jurisdiction. Every jurisdiction this site covers is listed, including those where the substance does not appear.
JurisdictionStatusScope and limitsCitation
United StatesFood and Drug AdministrationPermitted21 CFR 184.1278retrieved 2026-09-07
Codex AlimentariusCodex Alimentarius Commission / JECFANot listedDoes not appear on this jurisdiction’s permitted list. That is not the same as being prohibited.

What it is made from

Produced by fermentation or chemical synthesis, and present naturally in cultured dairy products. The occupational lung disease found in flavouring plant workers came from inhaling the vapour at industrial concentrations; it is a workplace air question rather than one about eating the food.

  • Vegan
  • Vegetarian
CAS registry number
431-03-8
InChIKey
QSJXEFYPDANLFS-UHFFFAOYSA-N
PubChem
CID 650

Every name it appears under

42 recorded names. A label may use any of them.

CAS registry number

  • 1173018-75-1
  • 431-03-8

As it appears in regulation

  • Diacetyl

Other names

  • 2,3 butandione
  • 2,3 Butanedione
  • 2,3-Butadione
  • 2,3-butandione
  • 2,3-Butanedione
  • 2,3-Butanedione (8CI,9CI)
  • 2,3-Butanedione, 97%
  • 2,3-Butanedione, analytical standard
  • 2,3-Butanedione-13C2
  • 2,3-diketobutane
  • 2,3-dioxobutane
  • 4-01-00-03644 (Beilstein Handbook Reference)
  • Biacetyl
  • Biacetyl; BDM
  • BRN 0605398
  • BUO
  • Buta-2,3-dione
  • butadione
  • Butan-2,3-dione
  • butane 2
  • butane-2
  • Butane-2,3-dione
  • Butanedione
  • CAS-431-03-8
  • CCRIS 827
  • Diacetyl
  • Diacetyl (natural)
  • Diacetyl 1000 microg/mL in Methanol
  • Diacetyl, natural, >=95%
  • Diketobutane
  • dimethyl diketone
  • Dimethyl glyoxal
  • dimethylglyoxal
  • FEMA No. 2370
  • Glyoxal, dimethyl-
  • HSDB 297
  • InChI=1/C4H6O2/c1-3(5)4(2)6/h1-2H
  • WLN: 1VV1

Systematic names

  • butane-2,3-dione

Hazard reference values

No reference value for this substance in the sources we hold.

Evidence and how bodies read it

Studies, and the differing conclusions regulators drew from them, are curated by hand rather than machine-read, and none has been written for this substance yet.

Sources for this page

  • ecfr retrieved 2026-09-07

Full licence terms and publisher details on Sources. How this page is built and updated: Method.

Machine-readable:/api/v1/additives/diacetyl.json