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|Section2= |Section3= |Section7= |Section8= }} 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 HO2CCHCHCO2H. Maleic acid is the ''cis''-isomer of butenedioic acid, whereas fumaric acid is the ''trans''-isomer. It is mainly used as a precursor to fumaric acid, and relative to its parent maleic anhydride, maleic acid has few applications. == Physical properties == Maleic acid is a less stable molecule than fumaric acid. The difference in ''heat of combustion'' is 22.7 kJ·mol−1. The heat of combustion is -1355 kJ/mole.〔(Maleic Anhydride, Maleic Acid, and Fumaric Acid ), Huntsman Petrochemical Corporation〕 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). Both properties of maleic acid can be explained on account of the intramolecular hydrogen bonding that takes place in maleic acid at the expense of intermolecular interactions, and that are not possible in fumaric acid for geometric reasons. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「maleic acid」の詳細全文を読む スポンサード リンク
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