Question

An example of electrophilic substitution reaction is :

• A. Chlorination of methane
• B. Conversion of methyl chloride to methyl alcohol
• C. Nitration of benzene
• D. Formation of ethylene from ethyl alcohol.
• E.

Hint:

Remember that benzene rings are highly electron-dense and generally repel nucleophiles, making them prime targets for electrophilic attack. Common electrophilic aromatic substitution reactions include nitration, halogenation, sulfonation, and Friedel-Crafts alkylation/acylation.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Electrophilic substitution reactions are characteristic of aromatic compounds, such as benzene. In these reactions, an electrophile (an electron-seeking species) substitutes one of the hydrogen atoms on the aromatic ring, preserving the stable aromatic system.

Step 2: Detailed Explanation:
Let's analyze each of the given options:
(A) Chlorination of methane: This reaction proceeds via a free-radical mechanism under the presence of sunlight or heat. It is a free-radical substitution reaction, not electrophilic.
(B) Conversion of methyl chloride to methyl alcohol: This involves the reaction of methyl chloride with an aqueous alkali (like NaOH). The hydroxide ion (\(OH^-\)) acts as a nucleophile, replacing the chloride ion. This is a nucleophilic substitution reaction (specifically $S_N2$).
(C) Nitration of benzene: Benzene reacts with a mixture of concentrated nitric acid (\(HNO_3\)) and concentrated sulfuric acid (\(H_2SO_4\)). The sulfuric acid acts as a catalyst to generate the nitronium ion (\(NO_2^+\)), which is a strong electrophile. This nitronium ion then attacks the electron-rich benzene ring, substituting a hydrogen atom. This is a classic example of an electrophilic aromatic substitution.
(D) Formation of ethylene from ethyl alcohol: This reaction involves heating ethyl alcohol with concentrated sulfuric acid, which acts as a dehydrating agent to remove a molecule of water, forming a double bond. This is an elimination reaction.

Step 4: Final Answer:
Therefore, the nitration of benzene is the correct example of an electrophilic substitution reaction.