Permanganate

Permanganate (also Tetraoxomanganate (VII ) ) are salts with the singly negatively charged anion MnO4 -.

Structure

Permanganate are derived from the constant only in dilute aqueous solution permanganic from the molecular formula HMnO4. Permanganic can concentrate in vacuo to about 20 %. It is a strong acid having a pKa of -2.25. A very pure solution of permanganic can be obtained, among others, by dropwise addition of the underlying anhydride Manganese ( VII ) oxide, with the empirical formula Mn2O7, to a large amount of chilled water.

Salts

Major salts are, for example:

• Potassium permanganate KMnO4
• Calcium permanganate Ca ( MnO4 ) 2
• Rubidiumpermanganat RbMnO4

Properties

The permanganate are water soluble and form purple solutions, the best known being the potassium permanganate. They are strong oxidizing agents. With their help, for example, alkenes via the corresponding glycols in ketones and / or carboxylic acids can be converted, formic and oxalic acid to carbon dioxide and aldehydes into carboxylic acids. A typical reaction of permanganate as the oxidizing agent, the oxidation of concentrated hydrochloric acid to chlorine gas, wherein the permanganate itself to manganese (II) is reduced:

Iron ( II) sulfate solution reacts with permanganate in acid to manganese (II ) - and iron salts (III) under basic conditions to manganese (IV ) oxide ( manganese dioxide ).

In analytics permanganate are used in redox titrations, see Manganometry.

Use

Permanganate also be used for purification of organic liquids as well as the exhaust air and waste water in the pharmaceutical and chemical industry.