Question

Out of benzene, m-dinitrobenzene and toluene which will undergo nitration most easily and why?

Answer 1

Question:

Out of benzene, m-dinitrobenzene and toluene, which will undergo nitration most easily and why?

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Answer:

Toluene will undergo nitration most easily.

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Explanation:

The ease of nitration (an electrophilic substitution reaction) depends on the electron density of the benzene ring. Groups attached to the ring may either activate or deactivate it.

• Toluene:
  The methyl group (–CH₃) is an electron-donating group. It increases the electron density of the benzene ring through +I effect and hyperconjugation, thereby activating the ring towards electrophilic substitution. Hence, nitration occurs most easily.
• Benzene:
  Benzene has no substituent to donate or withdraw electrons. Its reactivity towards nitration is moderate and lies between toluene and m-dinitrobenzene.
• m-Dinitrobenzene:
  Nitro groups (–NO₂) are strong electron-withdrawing groups. Two nitro groups greatly reduce the electron density of the ring, making it highly deactivated towards electrophilic substitution. Hence, nitration is very difficult. 

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Order of ease of nitration:

Toluene > Benzene > m-Dinitrobenzene