Organic Chemistry: Alkenes and Alkynes Reaction

What is the chemical name for the reaction of alkenes with potassium permanganate?

What is the product formed when alkynes are oxidized by potassium permanganate?

The reaction between alkenes and potassium permanganate is fast.

Why does potassium permanganate react with alkenes and alkynes, but not with alkanes and aromatic rings?

What color is the precipitate of manganese oxide formed during the reaction of potassium permanganate with alkenes and alkynes?

What is the primary reason for the slow reaction rate between potassium permanganate and hydrocarbons?

What is the difference between a geminal diol and a geminal diketone?

Geminal diols and diketones can be further oxidized by permanganates under harsh conditions to form manganese dioxide.

What is the purpose of using different hydrocarbons in the procedure described?

Describe the observation that indicates a positive reaction between potassium permanganate and a hydrocarbon.

In the procedure, why does the permanganate solution remain purple when hexane and toluene are used?

Reaction with Potassium Permanganate

Alkenes can be oxidized to geminal diols using dilute aqueous potassium permanganate. Geminal diols have two hydroxyl groups on adjacent carbon atoms.
Alkynes can be oxidized to geminal diketones using the same method.
The reaction produces a brown precipitate of manganese dioxide (MnO2).
This reaction happens at the interface between the water and hydrocarbon solutions as neither substance is soluble in the other.
Reaction time is slow, requiring several minutes for the brown precipitate to form.
Example: The oxidation of 3-hexene to 3,4-hexanediol occurs with the consumption of purple potassium permanganate. This is followed by the formation of a brown precipitate of manganese dioxide
Example: The oxidation of 3-hexyne to 3,4-hexanedione involves a similar process.

Procedure

Use four test tubes labeled for different hydrocarbons (hexane, cyclohexene, 1-hexyne, and toluene).
Add 10 drops of each hydrocarbon to the respective test tubes.
Add 10 drops of 1% aqueous potassium permanganate to each tube.
Mix the contents well after addition.
Observe the results:
- Hexane and toluene do not react; the purple color of permanganate persists.
- Cyclohexene and 1-hexyne react; a reaction occurs, indicated by the disappearance of the purple solution and formation of brown manganese dioxide precipitate at the liquid interface,
- Observe the appearance of brown precipitates in the test tubes after 5 minutes of intermittent agitation.

Explore the oxidation of alkenes and alkynes using dilute aqueous potassium permanganate. This quiz covers key concepts such as the formation of geminal diols and diketones, as well as the reaction dynamics and precipitate formation. Test your understanding of this important organic reaction!