| Section2 = | Section3 = | SPhrases = }} }} Diacetyl (IUPAC systematic name: butanedione or 2,3-butanedione)'s a natural byproduct of fermentation. It's a vicinal diketone (two C=O groups, side-by-side) with the molecular formula C4H6O2. Diacetyl occurs naturally in alcoholic beverages and's added to some foods to impart a buttery flavor. In food products Diacetyl and acetoin are two compounds that give butter its characteristic taste. Because of this, manufacturers of margarines or similar oi… (More on Diacetyl)