hexanedioic

Hexanedioic acid, better known as adipic acid, is a dicarboxylic acid with the formula C6H10O4. It consists of a six-carbon chain bearing carboxyl groups at each end (HOOC-(CH2)4-COOH).

Nomenclature: IUPAC name hexanedioic acid; common name adipic acid; other names include 1,6-hexanedioic acid.

Production: Adipic acid is produced industrially by the oxidation of cyclohexanone and cyclohexanol (KA oil) using air or catalytic systems. The process yields adipic acid after purification. When nitric acid is used as an oxidant, nitrous oxide is formed as a byproduct, raising environmental concerns. Ongoing refinements seek to reduce emissions and to develop alternative routes.

Applications: It is the principal monomer for the production of nylon-6,6 (polyamide 66), formed by reaction with hexamethylene diamine. Adipic acid is also used in the manufacture of plasticizers, polyurethanes, coatings, and specialty polymers. In food, adipic acid is used as an acidity regulator (E355).

Properties and handling: Adipic acid is a white crystalline solid with a melting point around 152–154°C. It is sparingly soluble in water and relatively stable under ordinary conditions. It is an irritant and should be handled with appropriate personal protective equipment to avoid inhalation, skin, and eye contact.

Environmental notes: The production of adipic acid is a notable source of nitrous oxide, a greenhouse gas. Efforts in industry and research focus on reducing emissions and exploring alternative, potentially more sustainable production pathways.