Dihydroxylation of Alkenes
Cis-dihydroxylation of Alkenes: Laboratory Application
The Baeyer test checks for double bonds. In this test, a cold solution of potassium permanganate is added to the liquid to be tested. A color change from purple to colorless is indicative of the presence of double bonds.
Preparation of cis-cyclohexan-1,2-diol with potassium permanganate:
An ethanol solution of cyclohexene, potassium permanganate and magnesium sulfate is placed in a three-neck flask fitted with a thermometer, dropping funnel and stirrer and cooled in an ice-salt mixture. Water is added at such a rate not allowing the temperature to rise above 5. After two hours, manganese dioxide is removed by filtration and the filtrate is evaporated to give the desired product.