MCPBA (Warning: oxidant may be explodey)

Meta-chloroperbenzoic acid is a common organic oxidant used in synthesis. It is popular in part because it is very easy to handle; another common peracid, peracetic acid, is a liquid.


Like many peroxides, it's somewhat shock sensitive. The mixture sold as MCPBA is actually only about 70-75% MCPBA. The balance is MCBA - meta-chlorobenzoic acid, and water. This serves to desensitize the mixture to shock somewhat.


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I used this oxidant in nitroxide chemistry. It works best in chlorinated solvents and is quite a mild oxidant as well as oxygen donor. -NH(R) to -NOH(R) hydroxylamine for example is easily possible. And then further oxidation to the -N-O.(R) nitroxide radical usually ensues.

It is also good for forming nitro groups from primary amines. Gentle reflux with 4 equivs of mcpba in CHCl3 and watch the colour change to blue and then to yellow - and it's done.

Very very versatile reagent.

It's fairly dangerous if purified (by mild base extraction) and then dried. It also can exist in a Peroxy Anhydride form, which forms shock and heat sensitive crystals.