15.0 Nitration

  Alkyl Halides and Aryl Halides

This is the process of heating chlorobenzene with a mixture of concentrated sulphuric acid and concentrated nitric acid. For example, on heating chlorobenzene with concentrated sulphuric acid and concentrated nitric acid $1$-chloro-$4$-nitrobenzene is obtained as the major product and $1$-chloro-$2$-nitrobenzene is obtained as the minor product.

Mechanism:

Step 1: Generation of nitronium ion (electrophile)

$$HN{O_3} + 2{H_2}S{O_4} \to N{O_2}^ + \;\left( {{\text{Nitronium ion - Electrophile}}} \right) + {H_3}{O^ + } + 2HS{O_4}^ - $$

Step 2: Attack of nitronium ion at ortho and para positions

Step 3: Loss of proton, formation of $2$-Nitrobenzene and $4$-Nitrobenzene