Green Chemistry Education Network
In one of our intro organic/Biochem labs, the students use a 2% potassium dichromate solution to distinguish between alcohols. Does anyone use an alternative?
Potassium permanganate (KMnO4) is a good alternative to potassium dichromate. The tertiary alcohol can not be oxidized, and will not use any of the KMnO4, so the solution remains deep purple. For the Secondary alcohol, it will oxidize to a ketone with the KMnO4, having the KMnO4 reduced to the MnO2 which is brown in color. The primary alcohol is oxidized twice to an aldehyde then a carboxylic acid to turn the KMnO4 to colorless manganese ions.