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.