Question

Cyclopentene on treatment with alkaline potassium permanganate gives
A. Cyclopentanol
B. Trans 1, 2-cyclopentanediol
C. Cis 1, 2-cyclopentanediol
D. 1:1 mixture of cis and Trans-1,2-cyclopentanediol

Answer 1

Hint: Cycloalkenes are ring compounds with one or more double bonds in the molecule. Cyclopentene is a type of cycloalkenes. Cyclopentene on treatment with alkaline potassium permanganate undergoes oxidation as alkaline potassium permanganate is a strong oxidising agent.

Complete Step by Step Answer:
Cycloalkenes are cyclic compounds possessing one or more double bonds in the molecule. Cyclopentene is a type of cycloalkenes.

Potassium manganate(VII) solution when added to sodium carbonate solution becomes little alkaline. The purple solution initially becomes dark green and then develops a dark brown precipitate. Alkaline potassium permanganate is a strong oxidising agent which undergoes reduction itself.

Under an alkaline climate, the manganate (VII) ions are initially reduced to green manganate (VI) ions.
Manganate(VII) ions are a powerful oxidising agent and oxidise cyclopentene to cis 1,2-cyclopentanediol.

The alkaline potassium manganate (VII) solution makes the cyclopentene undergo oxidation by breaking down the carbon-carbon double bond and altering it with two bonds in which carbon is attached to the hydroxyl group. This is a cis isomer because two bonds in which carbon is attached to the hydroxyl group
bonds are on the same side.

The reaction happens as follows:-

Image: Conversion of cyclopentene into cis 1, 2-cyclopentanediol.

So, option C is correct.

Note: Alkenes react with potassium manganate(VII) solution. It is a purple colour solution. The colour modification relies on whether the potassium manganate(VII) is utilised in acidic or alkaline conditions.If the potassium manganate(VII) solution is mixed with dilute sulfuric acid, the purple solution becomes colourless.