but2enedioic

But-2-enedioic acid, also known as butenedioic acid, is an organic dicarboxylic acid with the molecular formula C4H4O4. Its structure features a four-carbon chain containing a carbon–carbon double bond with carboxyl groups on each end, giving HOOC-CH=CH-COOH. The molecule exists in two geometric isomers because of the double bond: the cis isomer known as maleic acid and the trans isomer known as fumaric acid.

The cis (maleic) and trans (fumaric) forms are the two geometric isomers of but-2-enedioic acid. They differ in shape and certain physical properties, leading to distinct chemical reactivities and applications. Both forms are colorless solids and can participate in typical dicarboxylate chemistry, including condensation reactions and hydrolysis of related anhydride derivatives.

Industrial production and derivatives: In industry, the related anhydride, maleic anhydride, is a common precursor. Hydrolysis of maleic anhydride yields maleic acid (the cis isomer). Fumaric acid (the trans isomer) can be obtained through isomerization of the cis form or via separate synthetic routes. But-2-enedioic acid and its derivatives are used as intermediates in the manufacture of polymers and resins, such as unsaturated polyesters and alkyd resins. Fumaric acid also serves as a food acidity regulator in various products.

Safety and handling: But-2-enedioic acid and its isomers are irritants to skin and eyes upon contact and should be handled with appropriate protective equipment. They should be stored in a cool, dry place away from bases and strong oxidizers.