Question

What is the action of following reagents on chlorobenzene? (i) conc. $HNO_3$, (ii) fuming $H_2SO_4$

Hint:

For haloarenes, the para isomer is almost always the major product due to less steric hindrance compared to the ortho isomer.

Answer 1

Step 1: Understanding the Concept:
Electrophilic substitution in haloarenes. Chlorine is ortho-para directing due to resonance effects, even though it is deactivating due to its inductive effect.
Step 3: Detailed Explanation:
When chlorobenzene is treated with a nitrating mixture (conc. \(HNO_3\) + conc. \(H_2SO_4\)), nitration occurs.
The nitro group (\(-NO_2\)) attaches to the ortho and para positions relative to the chlorine atom.
1-chloro-4-nitrobenzene (para isomer) is the major product due to less steric hindrance, and 1-chloro-2-nitrobenzene (ortho isomer) is the minor product.
Step 4: Final Answer: Chlorobenzene reacts with conc. \(HNO_3\) to give a mixture of o-nitrochlorobenzene and p-nitrochlorobenzene.