# Dihydroxylation of Alkenes

## Cis-dihydroxylation of Alkenes: Laboratory Application

Baeyer test:

The Baeyer test checks for . 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.

### Movie of double bond test

Fig.
Test for C=C double bonds

### Example

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$°C$. After two hours, manganese dioxide is removed by filtration and the filtrate is evaporated to give the desired product.

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