Concept:Nitration relies on the creation of a highly electrophilic, positively charged nitrogen species 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:- Concentrated sulfuric acid protonates nitric acid, forcing it to lose a water molecule.
- The resulting species is the nitronium ion, \( \text{NO}_2^+ \).
- This linear ion contains a central nitrogen with a full positive charge and empty orbitals, making it the aggressive electrophile that attacks the benzene pi cloud.
Why other options are incorrect:- \( \text{NO}^+ \) is the nitrosonium ion, used in nitrosation, not nitration.
- \( \text{NO}_3^+ \) and \( \text{HNO}_2^+ \) are not the stable active intermediates generated in standard nitrating mixtures.
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