| Verifiedrevid | 437792124 |
|---|---|
| Iupacname | potassium manganate(V) potassium tetraoxidomanganate(3−) |
Potassium hypomanganate is the inorganic compound with the formula K3MnO4. Also known as potassium manganate(V), this bright blue solid is a rare example of a salt with the hypomanganate or manganate(V) anion, where the manganese atom is in the +5 oxidation state. It is an intermediate in the production of potassium permanganate and the industrially most important Mn(V) compound.[1]
Properties
Potassium hypomanganate is oxidized in water to potassium manganate:[2]
- 2 K3MnO4 + H2O + 0.5 O2 → 2 KOH + 2 K2MnO4
However, it undergoes disproportionation in acidic solutions producing manganese dioxide and potassium permanganate.[2]
In the absence of moisture, it is stable up to 900 °C. Above that temperature, it decomposes to potassium oxide, manganese(II,III) oxide, and oxygen.[3]
Preparative routes
The solid salt can be produced by the reaction of potassium carbonate and manganese carbonate in the presence of oxygen at 800 °C.[2] However, in the industrial process of producing potassium permanganate, it is produced by fusing manganese dioxide and potassium hydroxide. The resulting hypomanganate further reacts with water to produce manganate.[1]
A solution of potassium hypomanganate is produced:
- by two-electron reduction of potassium permanganate with excess potassium sulfite;[4][5]
- MnO4− + SO3(2−) + H2O → MnO4(3−) + SO4(2−) + 2 H+
- by the single-electron reduction of potassium manganate with hydrogen peroxide in 10 M potassium hydroxide solution;[6]
- 2 MnO4(2−) + H2O2 + 2 OH− → 2 MnO4(3−) + O2 + 2 H2O
- by the single-electron reduction of potassium manganate with mandelate in 3–10 M potassium hydroxide solution;[7]
- 2 MnO4(2−) + C8H7O3− + 2 OH− → 2 MnO4(3−) + C8H5O3− + 2 H2O
- by disproportionation when manganese dioxide is dissolved in a concentrated solution of potassium hydroxide;[4]
- 2 MnO2 + 3 OH− → MnO4(3−) + MnOOH + H2O
The compound is unstable due to the tendency of the hypomanganate anion to disproportionate in all but the most alkaline solutions.[4][5]
References
- ^ Kenneth Pisarczyk (2005). "Manganese Compounds". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.1301140716091901.a01.pub2
- ^ Tupec, Josef (2001). Interoperational analytical control during the production of potassium permanganate (Diploma)
- ^ H. Peters; K.-H. Radeke; L. Till (1966). "Über das thermische Verhalten von Kaliummanganat(V), -(VI) und -(VII)" [About the thermal behavior of potassium manganate(V), -(VI) and -(VII)] (in German). Zeitschrift für anorganische und allgemeine Chemie. 346 (1-2): 1-11. doi:10.1002/zaac.19663460102
- ^ .
- ^ .
- ^ Lee, Donald G. & Chen, Tao (1989), "Oxidation of hydrocarbons. 18. Mechanism of the reaction between permanganate and carbon-carbon double bonds", J. Am. Chem. Soc.. 111 (19): 7534–38, doi:10.1021/ja00201a039.
- ^ Lee, Donald G. & Chen, Tao (1993), "Reduction of manganate(VI) by mandelic acid and its significance for development of a general mechanism of oxidation of organic compounds by high-valent transition metal oxides", J. Am. Chem. Soc.. 115 (24): 11231–36, doi:10.1021/ja00077a023.