Concept:Electrophilic aromatic substitution (nitration) requires a strong acid catalyst to generate the highly reactive nitronium ion (\( \text{NO}_2^+ \)) from nitric acid.
Formula:$$ \text{HNO}_3 + 2\text{H}_2\text{SO}_4 \rightleftharpoons \text{NO}_2^+ + \text{H}_3\text{O}^+ + 2\text{HSO}_4^- $$
Solution:- A 1:1 mixture of concentrated nitric acid (\( \text{HNO}_3 \)) and concentrated sulfuric acid (\( \text{H}_2\text{SO}_4 \)) is known as a nitrating mixture.
- Sulfuric acid acts as a stronger acid, protonating nitric acid and causing it to dehydrate, yielding the essential \( \text{NO}_2^+ \) electrophile.
Why other options are incorrect:- HCl, acetic acid, and phosphoric acid are not strong enough or suitable dehydrating agents to efficiently generate the nitronium ion for benzene nitration under these standard conditions.
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