Question

Explain by giving the example of chlorobenzene that chlorine is ortho- and para-directing in electrophilic aromatic substitution reactions.

Hint:

Halogens are deactivating but ortho/para-directing due to resonance.

Answer 1

Step 1: Electrophilic Substitution in Chlorobenzene:
Chlorine has a \(-I\) effect (electron-withdrawing) and a \(+M\) effect (electron-donating via resonance), making the ortho and para positions more reactive. 

Step 2: Example - Nitration of Chlorobenzene: \[ C_6H_5Cl + HNO_3 \xrightarrow{H_2SO_4} o-C_6H_4ClNO_2 + p-C_6H_4ClNO_2 \]