diacetyl

Also known as 2,3-butadione, Butadione, Butan-2,3-dione, Dimethyl glyoxal, Acetoacetaldehyde, 2,3-butandione, Butanedione [UN2346]

Diacetyl ( ; IUPAC systematic name: butanedione or butane-2,3-dione) is an organic compound with the chemical formula (CH3CO)2. It is a yellow liquid with an intensely buttery flavor. It is a vicinal diketone (two C=O groups, side-by-side). Diacetyl occurs naturally in alcoholic beverages and some cheeses and is added as a flavoring to some foods to impart its buttery flavor. Chronic inhalation exposure to diacetyl fumes is a causative agent of the lung disease bronchiolitis obliterans, commonly known as "popcorn lung".