Malonic acid is corrosive

Malonic acid

Malonic acid (Propanedioic acid) is a dicarboxylic acid, its esters and salts which are crystalline at room temperature Malonates (e.g. diethyl malonate, but also diethyl malonate).

History and occurrence

Malonic acid was discovered in 1858 during the oxidation of malic acid. The name is derived from lat. malus = Apple (plant genus)[5] from. Malonic acid is found in sugar beet juice. Malonic acid is a cell toxin that inhibits the citrate cycle (Krebs cycle) by inhibiting succinate dehydrogenase.

properties

Malonic acid forms colorless and odorless crystals that have a melting point of 136 ° C and easily dissolve in water. In its pure form, above the melting point, acetic acid is formed by splitting off carbon dioxide; in aqueous solution, this decarboxylation takes place from 70 ° C.[5]

If malonic acid is heated with strongly dehydrating agents, e.g. B. with phosphorus pentoxide, intramolecular dehydration results in poor yields of carbon suboxide[5], also called malonic anhydride.

Malonic acid is a CH-acidic compound, i. H. Due to the electron-withdrawing effect of the two carboxy groups, a proton can easily be split off from the central carbon.

Manufacturing

Malonic acid is produced, among other things, by reacting chloroacetic acid with sodium cyanide (NaCN) (Kolbe nitrile synthesis) and subsequent hydrolysis of the resulting cyanoacetic acid.[5]

use

Malonic acid derivatives are synthetic building blocks in the Knoevenagel condensation or the malonic ester synthesis and are used, for example, to produce barbituric acid and its derivatives. In particular, William Henry Perkin, Jr. succeeded. for the first time a cyclopropanation by reaction of the C-H-acidic malonic acid diethyl ester with 1,2-dibromoethane and two equivalents of sodium ethoxide. When mixtures of cyclic imines with malonic acid are heated, β-aminocarboxylic acids are formed.[6]

Malonate: Risk of confusion with malate and maleate

Malonate must not be confused with the acid anion of malic acid, the malate ion, or the anion of maleic acid, the maleate.

Individual evidence

  1. 1,01,11,2 Thieme Chemistry (Ed.): RÖMPP Online - Version 3.5. Georg Thieme Verlag KG, Stuttgart 2009.
  2. 2,02,12,22,32,42,5Entry to CAS no. 141-82-2 in the GESTIS substance database of the IFA, accessed on January 7, 2008 (JavaScript required).
  3. 3,03,13,2data sheet Malonic acid at Sigma-Aldrich, accessed on August 10, 2012.
  4. ↑ Since December 1, 2012, only GHS hazardous substance labeling has been permitted for substances. Until June 1, 2015, the R-phrases of this substance may still be used to classify preparations, after which the EU hazardous substance labeling is of purely historical interest.
  5. 5,05,15,25,3Römpp CD 2006, Georg Thieme Verlag 2006.
  6. ↑ Jürgen Martens, Jürgen Kintscher and Wolfgang Arnold: Synthesis and stereochemistry of new 2-substituted 4-thiazolidinyl acetic acids, in: Tetrahedron, 1991, 47, Pp. 7029-7036.

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