Final answer:
When alkenes react with KMnO4, oxidative cleavage or syndihydroxylation occurs, forming either diols under mild conditions or carboxylic acids and CO2 under hot, acidic conditions.
Step-by-step explanation:
In the reaction of alkenes with KMnO4 (potassium permanganate), a process known as oxidative cleavage occurs where the double bond of the alkene is broken and usually transformed into two carbonyl groups. If the reaction is done under mild, neutral conditions, such as with dilute KMnO4 at room temperature, diols (compounds with two hydroxyl groups) are often created in a reaction known as syn dihydroxylation. However, if the conditions are more vigorous, as with concentrated KMnO4 and heat, the reaction often leads to cleavage, breaking the carbon backbone at the double bond and forming carboxylic acids from internal carbons, and carbon dioxide from terminal carbons in the alkene chain. Example: 1) KMnO4, neutral condition: Alkene → Glycol/Diol. 2)KMnO4, acidic and hot condition: Alkene → Carboxylic acid(s) and/or CO2