butanedioic

Butanedioic acid, commonly known as succinic acid, is a dicarboxylic acid with the chemical formula C4H6O4 and the structural formula HOOC-CH2-CH2-COOH. It is a white, odorless crystalline solid that is soluble in water. The molecule contains two carboxyl groups at the ends of a four-carbon chain, giving it two dissociable protons with pKa values around 4.21 and 5.64, making it a diprotic acid. Succinic acid occurs naturally as an intermediate in the citric acid cycle and is present in trace amounts in many living organisms.

Industrial production of butanedioic acid is achieved mainly by oxidation of hydrocarbons derived from butane and related feedstocks, as well as by fermentation-based routes using carbohydrates. Purified succinic acid is used as a chemical building block: it serves as a precursor to esters, anhydrides, and polymers; it is a key intermediate in the synthesis of succinates and polyesters, and it finds applications in the pharmaceutical and cosmetic industries. In the food industry, succinic acid is used as an acidity regulator and flavor adjunct (E363).

The chemistry of butanedioic acid allows it to form a cyclic anhydride, succinic anhydride, upon heating. It can also form a variety of esters and salts. It is relatively nonvolatile and has low acute toxicity, but contact with skin and eyes should be avoided. It is incompatible with strong oxidizers and should be stored in a cool, dry place.