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Potassium Permanganate (Purple...burning purple)

By moleculeoftheday on July 9, 2007.

Potassium permanganate, or KMnO4, is one of the most well-known oxidizing agents in chemistry. Unfortunately, it's a bit like taking a gun to a knife fight...

One of the big downsides of permanganate is the fact that it's a very polar ion. Crown ethers to the rescue.

Permanganate is a beautiful purple color in solution (almost black as the solid, partly because it's such a rich purple, partly because of MnO2 contamination), which I maintain is responsible for at least part of its popularity. It is a beast, as I alluded to earlier - it will take toluene down to benzoic acid (or even generic alkylbenzenes). It has some milder oxidations - for instance, if you use it on an olefin on ice, it will supposedly give you the cis-vic-diol. Everybody just uses OsO4 for this if they're sane, as far as I know.

Permanganate will do one lively reaction that young children, sadly, aren't able to see anymore. If you build a wee pile of permanganate and dribble some glycerine in the center, you'll be rewarded with a beautiful purple flame. See here for one of the animations that "Chemistry Comes Alive!" hasn't snatched from the public web.

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Permanganate I've never really seen used in a real research laboratory - although I do remember the bright violet colour of a dilute solution in the school labs. It's too strong for general use and tends to chew everything up. Great oxidiser though. Other choices are the chromates (potassium dichromate), which are a bit more selective.

Your suggestion of crown ether complexation could give a more useable oxidant and one that can be used in organic environments, which would probably decrease it's power a bit too.