HOOCCH2CH2COOH

HOOCCH2CH2COOH is the structural formula for succinic acid, also known as butanedioic acid. It is a simple aliphatic dicarboxylic acid with two carboxyl groups at both ends of a four-carbon chain. In solution, succinic acid behaves as a weak dibasic acid with two pKa values, typically around 4.2 and 5.6, corresponding to successive deprotonations. It is a solid at room temperature, with a melting point near 187–189°C, and it is appreciably soluble in water, with solubility increasing with temperature.

Occurrence and metabolism: Succinic acid is a natural metabolite in many organisms. In cellular respiration, succinate is an intermediate of the citric acid (Krebs) cycle, formed from succinyl-CoA and subsequently oxidized to fumarate. These biochemical roles underpin its biological relevance, though free succinic acid is primarily encountered in industrial and commercial contexts rather than as a common metabolite.

Production and applications: Industrially, succinic acid can be produced by fermentation using microorganisms, or prepared via chemical routes from maleic anhydride or related one-step oxidations. It is used as a food additive (listed as E363 in some regions), an acidulant and buffering agent, and as a building block in the synthesis of polyesters, plasticizers, and specialty chemicals. In addition to its consumer uses, succinic acid serves as a precursor in pharmaceutical and cosmetic formulations.

Safety and regulation: Succinic acid is generally regarded as having low toxicity and is used in food and pharmaceutical applications within regulatory limits. Concentrated solutions can be irritating to skin and eyes, and standard handling precautions apply in industrial settings.