Permanganate
Permanganates (also tetraoxomanganates (VII) ) are salts with the single negatively charged anion MnO 4 - .
structure
Permanganate are derived from the constant only in dilute aqueous solution permanganic with the molecular formula HMnO 4 from. Permanganic acid can be concentrated up to about 20% in a vacuum. It is a strong acid with a pKa value of −2.25. A very pure solution of permanganic acid can be obtained, among other things, by adding dropwise the underlying anhydride manganese (VII) oxide with the empirical formula Mn 2 O 7 to a large amount of well-cooled water.
Salts
Important salts are:
- Potassium permanganate KMnO 4
- Calcium permanganate Ca (MnO 4 ) 2
- Rubidium permanganate RbMnO 4
- Magnesium permanganate Mg (MnO 4 ) 2
- Silver permanganate AgMnO 4
properties
The permanganates are water-soluble and form violet solutions, the best known is potassium permanganate . They are strong oxidizing agents . With their help, for example, alkenes can be converted into ketones or carboxylic acids via the corresponding glycols , formic and oxalic acids into carbon dioxide and aldehydes into carboxylic acids. A typical reaction of permanganate as an oxidizing agent is the oxidation of concentrated hydrochloric acid to chlorine gas , whereby the permanganate itself is reduced to manganese (II):
Iron (II) sulphate solution reacts with permanganate solution in acid to form manganese (II) and iron (III) salts, in basic to manganese (IV) oxide ( manganese dioxide ).
In analysis , permanganates are used for redox titrations , see manganometry .
use
Permanganates are also used to purify organic liquids, exhaust air and wastewater in the pharmaceutical and chemical industries . In the paraffin oxidation permanganates were used as catalysts used. In organic synthesis, potassium permanganate is reacted with alkenes to form cyclic manganate esters. The work-up gives cis -1,2-diols:
Individual evidence
- ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1618.
- ^ Gmelin's Handbook of Inorganic Chemistry; Volume Manganese C2.
- ↑ G. Wietzel: Production of synthetic fatty acids by oxidation of paraffinic hydrocarbons with molecular oxygen. In: Chemical Engineering Science. 3, 1954, pp. 17-IN4, doi : 10.1016 / S0009-2509 (54) 80003-0 .
- ↑ Joachim Buddrus, Bernd Schmidt: Fundamentals of Organic Chemistry , 5th Edition, de Gruyter Verlag, Berlin, 2015, p. 186, ISBN 978-3-11-030559-3 .