|Jmol-3D images||Image 1|
|Molar mass||104.06 g mol−1|
|Melting point||135–136 °C|
|Solubility in water||Miscible|
|Acidity (pKa)||pKa1 = 2.83
pKa2 = 5.69
|Related carboxylic acids||acetic acid
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Malonic acid (IUPAC systematic name: propanedioic acid) is a dicarboxylic acid with structure CH2(COOH)2. The ionized form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid's diethyl ester. The name originates from the Greek word μᾶλον (malon) meaning 'apple'.
The calcium salt of malonic acid occurs in high concentrations in beetroot. It exists in its normal state as white crystals. Malonic acid is the classic example of a competitive inhibitor: It acts against succinate dehydrogenase (complex II) in the respiratory electron transport chain.
Sodium carbonate generates the sodium salt, which is then reacted with sodium cyanide to provide the cyano acetic acid salt via a nucleophilic substitution. The nitrile group can be hydrolyzed with sodium hydroxide to sodium malonate, and acidification affords malonic acid.
Malonic acid was first prepared in 1858 by the French chemist Victor Dessaignes (1800-1885) via the oxidation of malic acid.
In a well-known reaction, malonic acid condenses with urea to form barbituric acid. Malonic acid is also frequently used as an enolate in Knoevenagel condensations or condensed with acetone to form Meldrum's acid. The esters of malonic acid are also used as a −CH2COOH synthon in the malonic ester synthesis.
Additionally, the coenzyme A derivative of malonate, malonyl-CoA, is an important precursor in fatty acid biosynthesis along with acetyl CoA. Malonyl CoA is formed from acetyl CoA by the action of acetyl-CoA carboxylase, and the malonate is transferred to an acyl carrier protein to be added to a fatty acid chain.
- pKa Data Compiled by R. Williams (pdf; 77 kB)
- Nathan Weiner, "Malonic acid", Org. Synth.; Coll. Vol. 2: 376
- Dessaignes (1858) "Note sur un acide obtenu par l'oxydation de l'acide malique" (Note on an acid obtained by oxidation of malic acid), Comptes rendus, 47 : 76-79.
- Dessaignes (1858) "Ueber eine durch Oxydation der Aepfelsäure erhaltene Säure" (On an acid obtained by oxidation of malic acid) Annalen der Chemie und Pharmacie, 107 : 251-254.
- pH-Spectrum of Disodium Malonate
- pH-Spectrum of Malonate-copper-complex
- Calculator: Water and solute activities in aqueous malonic acid