Permanganate

Permanganate
"MnO4" redirects here. For the manganate ion MnO42−, see Manganate.
The structure of the manganate(VII) anion

A permanganate is the general name for a chemical compound containing the manganate(VII) ion, (MnO4−). Because manganese is in the +7 oxidation state, the permanganate(VII) ion is a strong oxidizing agent. The ion has tetrahedral geometry.[1] Permanganate solutions are purple in color and are stable in neutral or slightly alkaline media.

In an acidic solution, permanganate(VII) is reduced to the colourless +2 oxidation state of the manganese(II) (Mn2+) ion.

8 H+ + MnO4− + 5 e− → Mn2+ + 4 H2O

In a strongly basic solution, permanganate(VII) is reduced to the green +6 oxidation state of the manganate MnO42−.

MnO4− + e− → MnO42−

In a neutral medium however, it gets reduced to the brown +4 oxidation state of manganese dioxide MnO2.

2 H2O + MnO4− + 3 e− → MnO2 + 4 OH−

Contents

Production

Permanganates can be produced by oxidation of manganese compounds such as manganese chloride or manganese sulfate by strong oxidizing agents, for instance, sodium hypochlorite or lead dioxide:

2 MnCl2 + 5 NaClO + 6 NaOH → 2 NaMnO4 + 9 NaCl+ 3 H2O
2 MnSO4 + 5 PbO2+ 3 H2SO4 → 2 HMnO4 + 5 PbSO4 + 2 H2O

It may also be produced by the dismutation of manganates, with manganese dioxide as a side-product:

3 Na2MnO4 + 2 H2O → 2 NaMnO4 + MnO2 + 4 NaOH

Properties

Permanganates(VII) are salts of permanganic acid. Permanganate(VII) is a strong oxidizer, and similar to perchlorate. It is therefore in common use in qualitative analysis that involves redox reactions (permanganometry). Besides this, it is stable.

It is a useful reagent, though with organic compounds, not very selective.

Manganates(VII) are not very stable thermally. For instance, potassium permanganate decomposes at 230 °C to potassium manganate and manganese dioxide, releasing oxygen gas:

2 KMnO4 → K2MnO4 + MnO2 + O2

A permanganate can oxidize an amine to a nitro compound,[2][3] an alcohol to a ketone,[4] an aldehyde to a carboxylic acid,[5][6] a terminal alkene to a carboxylic acid,[7] oxalic acid to carbon dioxide,[8] and an alkene to a diol.[9] This list not exhaustive.

In alkene oxidations one intermediate is a cyclic Mn(V) species:

Permanganate oxidation mechanism

Compounds

See also

  • Perchlorate, a similar ion with a chlorine(VII) center
  • Chromate, which is isoelectronic with permanganate

References

  1. ^ Sukalyan Dash, Sabita Patel and Bijay K. Mishra (2009). "Oxidation by permanganate: synthetic and mechanistic aspects". Tetrahedron 65 (4): 707–739. doi:10.1016/j.tet.2008.10.038. 
  2. ^ A. Calder, A. R. Forrester1, and S. P. Hepburn (1972), "2-methyl-2-nitrosopropane and its dimer", Org. Synth. 6: 803, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV6P0803 ; Coll. Vol. 52: 77 
  3. ^ Nathan Kornblum and Willard J. Jones (1963), "4-nitro-2,2,4-trimethylpentane", Org. Synth. 5: 845, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV5P0845 ; Coll. Vol. 43: 87 
  4. ^ J. W. Cornforth (1951), "Ethyl pyruvate", Org. Synth. 4: 467, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV4P0467 ; Coll. Vol. 31: 59 
  5. ^ R. L. Shriner and E. C. Kleiderer (1930), "Piperonylic acid", Org. Synth. 2: 538, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV2P0538 ; Coll. Vol. 10: 82 
  6. ^ John R. Ruhoff (1936), "n-heptanoic acid", Org. Synth. 2: 315, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV2P0315 ; Coll. Vol. 16: 39 
  7. ^ Donald G. Lee, Shannon E. Lamb, and Victor S. Chang (1981), "Carboxylic acids from the oxidation of terminal alkenes by permanganate: nonadecanoic acid", Org. Synth. 7: 397, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV7P0397 ; Coll. Vol. 60: 11 
  8. ^ Kovacs KA, Grof P, Burai L, Riedel M (2004). "Revising the Mechanism of the Permanganate/Oxalate Reaction". J. Phys. Chem. A 108 (50): 11026. doi:10.1021/jp047061u. 
  9. ^ E. J. Witzemann, Wm. Lloyd Evans, Henry Hass, and E. F. Schroeder (1931), "dl-glyceraldehyde ethyl acetal", Org. Synth. 2: 307, http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV2P0307 ; Coll. Vol. 11: 52 

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  • permanganate — [ pɛrmɑ̃ganat ] n. m. • 1848; de permanganique ♦ Chim. Sel de l acide permanganique, inconnu à l état libre. Permanganate de potassium (KMnO4). Les permanganates de potassium et de calcium ont des propriétés antiseptiques. Cour. Permanganate de… …   Encyclopédie Universelle

  • Permanganate — Per*man ga*nate, n. (Chem.) A salt of permanganic acid. [1913 Webster] {Potassium permanganate}. (Chem.) See {Potassium permanganate}, under {Potassium}. [1913 Webster] …   The Collaborative International Dictionary of English

  • Permanganāte — Permanganāte, die Salze der Übermangansäure, z. B. Kaliumpermanganat, übermangansaures Kali …   Meyers Großes Konversations-Lexikon

  • Permanganate — Permanganate, s. Mangansäuren …   Lexikon der gesamten Technik

  • Permanganate — Permanganāte, die Salze der Übermangansäure …   Kleines Konversations-Lexikon

  • Permanganate — Permanganate,   Salze der Permangansäure, HMnO4 (Manganverbindungen).   …   Universal-Lexikon

  • permanganate — [pər maŋ′gə nāt΄] n. a salt of permanganic acid containing the monovalent, negative radical MnO4: it is a strong oxidizing agent and is generally dark purple in color …   English World dictionary

  • Permanganate — La structure de l ion permanganate Le permanganate (MnO4 ) est l anion des sels de l acide permanganique. On parle souvent de permanganate pour désigner le permanganate de potassium. Les permanganates sont notamment utilisés pour la synthèse de… …   Wikipédia en Français

  • Permanganate — Permanganat Ion Permanganate (auch Tetraoxomanganate(VII)) sind Salze mit dem einfach negativ geladenen Anion MnO4−. Inhaltsverzeichnis 1 Struktur …   Deutsch Wikipedia

  • permanganate — noun Date: 1841 1. a salt containing the anion MnO4 ; especially potassium permanganate 2. the anion MnO4 of a permanganate …   New Collegiate Dictionary

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