Maleic acid is an organic compound that is a dicarboxylic acid, a molecule with two carboxyl groups. Its chemical formula is C4H4O4. Maleic acid is the cis-isomer of butenedioic acid, whereas fumaric acid is the trans-isomer.
Maleic acid (MA) is a dicarboxylic acid that undergoes esterification with ethanol in the presence of cation-exchange resin catalysts to form diethyl maleate. Its crystalline structure has been analyzed..