Sorbic acid, or 2,4-hexadienoic acid, is the natural organic compound used as the food preservative. It has the chemical formula CH3CH4CO2H. it is for a colourless solid that is slightly soluble in water together with sublimes readily. It was first isolated from the unripe berries of the Sorbus aucuparia rowan tree, hence its name.
The traditional route to sorbic acid involves condensation of malonic acid in addition to trans-butenal. It can also be prepared from isomeric hexadienoic acids, which are usable via a nickel-catalyzed reaction of allyl chloride, acetylene, and carbon monoxide. The route used commercially, however, is from crotonaldehyde and ketene. An estimated 30,000 tons are made annually.