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Potassium hypomanganate

Names
IUPAC names potassium manganate(V) potassium tetraoxidomanganate(3−)
Identifiers
3D model (JSmol)	Interactive image
ChemSpider	64887110
PubChem CID	118856760
CompTox Dashboard (EPA)	DTXSID20893219
InChI InChI=1S/3K.Mn.4O/q3*+1;-3;;;;Key: BABZALCEXXHDEO-UHFFFAOYSA-N
SMILES O=(=O)(=O)=O...
Properties
Chemical formula	K3MnO4
Molar mass	236.229 g·mol
Appearance	bright blue solid
Density	2.78 g/cm
Melting point	900 °C (1,650 °F; 1,170 K) (decomposes)
UV-vis (λmax)	670 nm (ε = 900 dm mol cm)
Related compounds
Other anions	Potassium manganate Potassium permanganate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references

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.

Properties

Potassium hypomanganate is oxidized in water to potassium manganate:

2 K₃MnO₄ + H₂O + 0.5 O₂ → 2 KOH + 2 K₂MnO₄

However, it undergoes disproportionation in acidic solutions producing manganese dioxide and potassium permanganate.

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.

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. 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.

A solution of potassium hypomanganate is produced:

• by two-electron reduction of potassium permanganate with excess potassium sulfite;

MnO−4 + SO2−3 + H₂O → MnO3−4 + SO2−4 + 2 H

• by the single-electron reduction of potassium manganate with hydrogen peroxide in 10 M potassium hydroxide solution;

2 MnO2−4 + H₂O₂ + 2 OH → 2 MnO3−4 + O₂ + 2 H₂O

• by the single-electron reduction of potassium manganate with mandelate in 3–10 M potassium hydroxide solution;

2 MnO2−4 + C₈H₇O−3 + 2 OH → 2 MnO3−4 + C₈H₅O−3 + 2 H₂O

• by disproportionation when manganese dioxide is dissolved in a concentrated solution of potassium hydroxide;

2 MnO₂ + 3 OH → MnO3−4 + MnOOH + H₂O

The compound is unstable due to the tendency of the hypomanganate anion to disproportionate in all but the most alkaline solutions.

References

1. ^ 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.
2. ^ Kenneth Pisarczyk (2005). "Manganese Compounds". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.1301140716091901.a01.pub2.
3. ^ Tupec, Josef (2001). Interoperational analytical control during the production of potassium permanganate (PDF) (Diploma thesis).
4. 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)]. Zeitschrift für anorganische und allgemeine Chemie (in German). 346 (1–2): 1–11. doi:10.1002/zaac.19663460102.
5. ^ Cotton, F. Albert; Wilkinson, Geoffrey (1980), Advanced Inorganic Chemistry (4th ed.), New York: Wiley, p. 746, ISBN 0-471-02775-8.
6. ^ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 1221–22. ISBN 978-0-08-022057-4..
7. 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.

• Potassium compounds
• Manganese(V) compounds