Maleic acid
- Cis- butenedioic
- Cis- ethylene dicarboxylic acid
- Toxilsäure
- (Z)- butenedioic
White solid
Fixed
1.59 g · cm -3
Decomposition> 135 ° C
Decomposition> 135 ° C
1.9 and 6.5
- Well in water: 788 g · l-1 (25 ° C)
- In xylene: 163.2 g · l -1 ( 29.7 ° C)
Attention
-789.4 KJ / mol
Template: Infobox chemical / molecular formula search available
Maleic acid is the common name for cis- butenedioic (also cis- ethylene dicarboxylic acid or Toxilsäure called ), a dicarboxylic acid. Its salts are called times ( in ) ates. The isomeric trans form is called fumaric acid.
Production
Maleic acid is produced industrially from maleic anhydride; the anhydride is in turn synthesized by the catalytic oxidation of benzene or n-butane.
Properties
Physical Properties
Maleic acid forms of colorless crystals at room temperature. When heated, decomposition is observed above 135 ° C. It is readily soluble in water and reacts in highly acidic: the dibasic acid has a PKS1 of 1.9 and a pKa2 of 6.5. The compound dissolves very well in water, the solubility increases with increasing temperature greatly.
Chemical Properties
Prolonged heating at 150 ° C and under UV irradiation, the maleic acid is isomerized to the more stable fumaric acid. When heated, it turns into maleic anhydride with elimination of water. The anhydride is formed when dissolved in water again maleic acid.
1874 The spatial structure of the chemical behavior - the anhydride - derived.
Use
Maleic acid is used for the preparation of polymers, resins, and maleic acid esters, for finishing and in the dyeing of cotton and as an ingredient of descaling based on sulfamic acid and citric acid, which is intended to counteract a fast re- calcification.
In medicine solutions of the maleate of antihistamines are used as injectable drugs for acute use. In the preparative chemistry of maleic acid is commonly used as an agent for the Diels- Alder reaction.
Maleate: confusion with malonate and malate
Maleate should not be confused with the acid anion of malic acid, the malate ion, or the anion of malonic acid, the malonate.