[{"from": "human", "value": "Please give me some details about this molecule. [C][C][=Branch1][C][=O][C][=Branch1][C][=O][C]"}, {"from": "gpt", "value": "The molecule is a natural by-product of secondary or malolactic fermentation. It is a vicinal diketone (two C=O groups, side-by-side) with the molecular formula C4H6O2. Carrier of aroma of butter, vinegar, coffee, and other foods. Beer sometimes undergoes a diacetyl rest, which entails waiting two or three days after fermentation is complete, to allow the yeast to absorb the diacetyl it produced earlier in the fermentation cycle. The makers of some wines, such as chardonnay, deliberately promote the production of diacetyl because of the feel and flavors it imparts."}]