Question

What is the product formed when chlorobenzene undergoes nitration with concentrated $HNO_3$ and $H_2SO_4$?

• A. Nitrobenzene
• B. 1,3-Dinitrobenzene
• C. o- and p-Nitrochlorobenzene
• D. Chlorobenzene sulfonic acid

Hint:

Important Directing Effects in Aromatic Substitution: Halogens ($-Cl$, $-Br$, $-I$) are ortho-para directing but deactivating. Examples: Chlorobenzene nitration $\rightarrow$ o- and p-nitrochlorobenzene.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Nitration of benzene derivatives is an Electrophilic Aromatic Substitution (EAS) reaction. The existing substituent on the ring (in this case, Chlorine) determines where the new nitro group ($-NO_2$) will be attached.
Step 2: Detailed Explanation:
1. Directing Influence: The Chlorine atom has lone pairs of electrons that can be delocalized into the ring via resonance. This makes Chlorine an ortho- and para-directing group.
2. Deactivation: Although it is $o/p$ directing, Chlorine is slightly deactivating due to its high electronegativity ($-I$ effect).
3. The Reaction: Chlorobenzene reacts with a nitrating mixture ($HNO_3 + H_2SO_4$) to produce a mixture of 1-chloro-2-nitrobenzene (ortho) and 1-chloro-4-nitrobenzene (para).
4. Major Product: The para-isomer is usually the major product due to less steric hindrance.
Step 3: Final Answer
The products formed are o- and p-Nitrochlorobenzene.