Malonic acid
Propandioic
Colorless crystals
Fixed
1.62 g · cm -3
136 ° C
Decomposition from 140 ° C
0.1 Pa ( 18.5 ° C)
- PKS1 = 2.83
- PKa2 = 5.69
- Well in water ( 1390 g · l-1, 22 ° C ), pyridine, ethanol and diethyl ether
- Insoluble in benzene
Risk
1310 mg · kg -1 ( LD50, rat, oral)
Template: Infobox chemical / molecular formula search available
Malonic acid ( propanedioic acid ) is a crystalline at room temperature, the dicarboxylic acid, its esters and salts are known as malonates (e.g., diethyl malonate ( malonic acid diethyl ester ) ).
History and habitat
Malonic acid was discovered in 1858 in the oxidation of the malic acid. The name derives from the Latin malum = apple ( plant genus ). Malonic acid is found in beet juice. Malonic acid is a cell poison that inhibits by inhibition of succinate dehydrogenase the course of the citric acid cycle (Krebs cycle).
Properties
Malonic acid forms colorless, odorless crystals that hold and easy to dissolve in water has a melting point of 136 ° C. In its pure form is created above the melting point by Kohlenstoffdioxidabspaltung acetic acid, found in aqueous solution, these decarboxylation from 70 ° C instead.
When heated with malonic acid produced strong dehydrating agents, such as with phosphorus, so by intramolecular elimination of water in poor yield carbon suboxide, also known as malonic.
Malonic acid is a CH-acidic compound, i.e., by the electron-withdrawing effect of the two carboxylic groups can be readily cleaved at the central carbon is a proton.
Production
Malonic acid is produced, among others, by the reaction of chloroacetic acid with sodium cyanide ( NaCN ) ( Kolbe nitrile synthesis ) and subsequent hydrolysis of the resulting cyanoacetic acid.
Use
Malonic acid derivatives are synthetic building blocks in the Knoevenagel condensation of malonic ester or synthesis and are used for example for the preparation of barbituric acid and derivatives thereof. In particular, William Henry Perkin, Jr. succeeded for the first time a cyclopropanation by reaction of the CH-acid diethyl malonate with 1,2- dibromoethane and two equivalents of sodium ethoxide. Upon heating of mixtures of cyclic imines with malonic acid caused β -amino acids.
Malonate: confusion with malate and maleate
Malonate should not be confused with the acid anion of malic acid, the malate ion, or the anion of maleic acid, the maleate.