Maleic acid
dicarboxylic acid
Maleic acid or cis-butenedioic acid is an organic compound that is a dicarboxylic acid, a molecule with two carboxyl groups. Its chemical formula is HO2CCH=CHCO2H. Maleic acid is the cis isomer of butenedioic acid, whereas fumaric acid is the trans isomer. Maleic acid is mainly used as a precursor to fumaric acid, and relative to its parent maleic anhydride, which has many applications.
Etymology
'Maleic acid' from the French acide maléique altered from acide malique, malic acid, from which it was synthesised. The word 'malic' is derived from Latin mālum, meaning 'apple'.
Physical properties
Maleic acid has a heat of combustion of −1,355.2 kJ/mol, −20.5 kJ/mol higher than that of fumaric acid. Maleic acid is more soluble in water than fumaric acid. The melting point of maleic acid (135 °C) is also much lower than that of fumaric acid (287 °C). As confirmed by X-ray crystallography, maleic acid is planar. Two normal hydrogen bonds are observed, one intramolecular and one intermolecular.
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This entry incorporates text from “Maleic acid” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.