Question

Cyclopentene on treatment with alkaline \(\mathrm{KMnO}_{4}\) gives (1) cyclopentanol (2) trans-1,2-cyclopentane diol (3) cis 1,2 -cyclopentane diol (4) mixture of \((2)\) and \((3)\)

Short answer

The product is cis-1,2-cyclopentane diol (Option 3).

Step-by-step solution

- Identify the reagent and reaction type

The reagent used in this reaction is alkaline \( KMnO_4 \). This is a strong oxidizing agent typically used to convert alkenes to diols through a process known as hydroxylation.

- Analyze the structure of cyclopentene

Cyclopentene is a five-membered cyclic alkene. It has a double bond between two of its carbon atoms, which can participate in the reaction with alkaline \( KMnO_4 \).

- Determine the diol formation

When cyclopentene reacts with alkaline \( KMnO_4 \), the double bond is cleaved, and each carbon that was part of the double bond gets an \( -OH \) group, resulting in the formation of a diol. Given that this is a cis-hydroxylation reaction, the product formed is cis-1,2-cyclopentane diol.

- Compare with given options

Upon reviewing the provided options, the correct identification of the product - cis-1,2-cyclopentane diol - matches option (3).

Key concepts

alkene hydroxylation

Alkene hydroxylation is an important reaction in organic chemistry. It involves the addition of hydroxyl groups (OH) to the carbon atoms involved in a double bond of an alkene.
The reaction is typically achieved using strong oxidizing agents such as potassium permanganate (KMnO4).
This process turns the alkene into a diol, which is a compound with two hydroxyl groups.
Hydroxylation can happen in either a syn or anti fashion. Syn addition leads to both hydroxyl groups being added to the same side of the double bond.
In the case of cyclopentene reacting with alkaline KMnO4, the hydroxylation occurs in a syn manner, resulting in a cis-diol.

cis-diol formation

Cis-diol formation occurs when two hydroxyl groups are added to the same side of a double bond during a chemical reaction.
In our case, cyclopentene reacts with alkaline KMnO4 (potassium permanganate). This reaction is known as syn-hydroxylation.
The syn-hydroxylation means that the OH groups attach to the same face of the double bond.
The product of this hydroxylation reaction with cyclopentene is cis-1,2-cyclopentane diol.
Because the hydroxyl groups are on the same side, it has the 'cis' configuration, where both hydroxyl groups are added to adjacent carbons.

oxidizing agents in organic chemistry

Oxidizing agents play a crucial role in organic reactions, especially in transforming the structure of hydrocarbons.
Alkaline KMnO4 is one such strong oxidizing agent. It is highly effective in converting alkenes into diols.
In oxidation reactions, KMnO4 typically adds hydroxyl groups across a double bond, breaking it and forming a diol.
The agents help to increase the oxygen content of the organic molecules by breaking the double bonds.
For cyclopentene, KMnO4's action forms cis-1,2-cyclopentane diol as it hydroxylates the double bond. This specificity shows how oxidizing agents can control the product configuration in organic reactions.