What is the action of KMnO4 with an unsaturated compound?

Answer 1

Potassium permanganate is an oxidant; the extent to which it will oxidize an alkene is a bit unpredictable and highly dependent on reaction conditions. Under harsh conditions (heat, base), KMnO4 will break the double bond and form a carboxylic acid or ketone where the bond was broken depending on the number of substituents. Terminal olefins form carbon dioxide. In less harsh conditions, KMnO4 might add alcohol groups to the sp2 carbons (in a syn addition).

Answer 2

KMnO4 can react with unsaturated compounds through a process called oxidative cleavage. The double or triple bond in the unsaturated compound is broken, and new functional groups are introduced. This reaction is often used to convert alkenes or alkynes into diols or carboxylic acids, respectively.