|Systematic name||Cis-butenedioic acid|
|Molar mass||116.072 g/mol|
|Density and phase||1.5±0.1 g/cm |
|Solubility in water||478.8 g/L at 20 C|
|Melting point||135 °C (275 °F; 408 K) (decomposes) |
|MSDS||Material Safety Data Sheet|
|Main hazards||Skin contacts, Eye contacts|
|RTECS number||OM9625000 |
| Except where noted otherwise, data are given for|
materials in their standard state (at 25 °C, 100 kPa)
Disclaimer and references
Maleic acid, also known as cis-butenedioic acid, has the chemical formula is C4H4O4. It is a dicarboxylic acid organic compound, which is a molecule with two carboxyl groups. Its chemical formula is HO2CCHCHCO2H. The colorless crystalline compound has a faint acidulous odor and a characteristic repulsive, astringent taste. It is primarily used as a precursor to fumaric acid, and relative to its parent maleic anhydride. 
Maleic Acid is an industrial raw material for the production of glyoxylic acid by ozonolysis. Maleic acid is an organic compound which is a dicarboxylic acid (molecule with two carboxyl groups). Maleic acid is the cis isomer of butenedioic acid, whereas fumaric acid is the trans isomer. The cis isomer is the less stable one of the two; the difference in heat of combustion is 22.7 kJ/mol. 
Maleic acid is an industrial raw material for the production of glyoxylic acid by ozonolysis. Maleic acid is an organic compound which is a dicarboxylic acid (molecule with two carboxyl groups). The molecule consists of an ethylene group flanked by two carboxylic acid groups. Maleic acid is the cis isomer of butenedioic acid, whereas fumaric acid is the trans isomer. The cis isomer is the less stable one of the two; the difference in heat of combustion is 22. 7 kJ/mol.  The decomposition of maleic acid in an aqueous solution over a bed of Y zeolite, which contains copper and sodium at around 200 ° C, occurs with 95% conversion. The selectivity of the zeolite catalyst to acrylic acid [79-10-7] is 91%. 
Physically, Maleic Acid is a colorless crystalline having a faint odor. Maleic Acid is a less stable than Fumaric Acid. Also, Maleic Acid is more soluble than Fumaric Acid in water .The melting point of maleic acid (135 °C) is also much lower than that of fumaric acid (287 °C).  Maleic acid is converted into maleic anhydride by dehydration, to malic acid by hydration, and to succinic acid by hydrogenation. It reacts with thionyl chloride or phosphorus pentachloride to give the maleic acid chloride (it is not possible to isolate the mono acid chloride). 
Maleic acid and fumaric acid are dicarboxylic acid isomers that have the same carbon skeleton. They both yield succinic acid (SA) by hydrogenation. Each can be converted to the identical anhydride by heat treatment, but maleic acid reacts much more rapidly. This, coupled with the fact that mild hydrolysis of maleic anhydride (MAnh) leads to maleic acid, is linked to the cis structure of maleic acid and to the trans structure of fumaric acid.
Historically, these two acids were first prepared in the 1830’s, but their commercial manufacture did not begin until almost one century later. Maleic acid was commercially available in 1928 and fumaric acid production began in 1932 using an acid-catalyzed isomerization of maleic acid process. Maleic anhydride can be commercially produced by the vapor-phase oxidation of benzene or butane using O2 as an oxidant. This reaction is very exothermic and CO and CO2 thus constitute the main by-products. The catalyst used in the production of maleic anhydride from butane is vanadium–phosphorus-oxide (VPO). The catalyst used for the conversion of benzene to maleic anhydride consists of supported vanadium oxide.
Maleic Acid is not considered as a dangerous compound. However, there are some dangers such as eye, skin, and respiratory tract irritation. Also, maybe harmful if swallowed or absorbed through the skin. Eye- can result in corneal injury. Contact with eye can cause severe irritation, and can cause eye burns. Skin- Contacts with skin can cause irritation and possible burns, especially if the skin is wet or moist. Also contacts with skin may cause dermatitis and can be harmful if absorbed through the skin. Ingestion- May cause kidney damage or be harmful if swallowed. Inhalation- Causes respiratory tract irritation. Chronic- Chronic exposure may cause kidney damage. 
Maleic Acid Video
- Maleic acid PubChem Last Modified. 24 February, 2018, Author unknown
- Maleic Aicd Chemicalbook Accessed. 3 March, 2018, Author unknown
- Maleic Acid Chemspider Accessed. March 3, 2018, Author unknown
- Maleic Acid Wikipedia 12 February, 2018, Author unknown
- Material Safety Data Sheet ScienceLab.com Created. 12 May, 2013
- Maleic Acid thechemicalcompany Accessed. March 19, 2018 Author Unknown.
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- Maleic acid PubChem Last Modified. 3 March, 2018. Author Unknown.
- Decomposition and decarboxylation maleic anhydride Course Hero Accessed. 3 March. 2018
- Maleic Acid Wikipedia Accessed. 6 March. 2018
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- Francesco Santarelli, Sébastien Paul, Franck Dumeignil, Fabrizio Cavani, Renato V Gonçalves Recent developments in maleic acid synthesis from bio-based chemicals Springer Link Created. 30 June, 2015
- Maleic Acid Material Safety Data Sheet Created. June 3, 1999