maleic

Maleic is a term used in chemistry to describe compounds that are derived from or related to maleic acid (cis-butenedioic acid) or its anhydride. The most common examples are maleic acid, maleic anhydride, and salts and esters known as maleates. The term is often encountered in polymer chemistry and organic synthesis.

Chemistry: Maleic acid is a dicarboxylic acid with a cis double bond; it exists predominantly in the cis configuration and forms salts with metals called maleates. Upon dehydration, it converts to maleic anhydride, a reactive cyclic anhydride. Maleic acid and maleic anhydride are both good dienophiles in Diels–Alder reactions and can undergo esterification to give various derivatives.

Production and uses: Industrially, maleic anhydride is produced mainly by oxidation of benzene or butane in air over vanadium- or phosphorus-oxide catalysts, then isolated by dehydration of the resulting diacid. Maleic acid can be prepared by partial oxidation or hydrolysis of derivatives, and can be converted to esters and salts. In industry, maleic anhydride is a key monomer in the production of alkyd and unsaturated polyester resins, coatings, and specialty polymers. It is also used as a crosslinking agent and to graft functional groups onto polymers to improve adhesion and compatibility.

Safety and handling: Maleic compounds can be irritants and corrosive. Inhalation or skin contact may cause irritation; fumes and dust should be avoided. Materials are typically handled with appropriate protective equipment and stored in tightly closed containers.