Question:
Which of the following is most reactive towards electrophilic substitution:
Which of the following is most reactive towards electrophilic substitution:
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Reactivity order: Pyrrole > Furan > Thiophene > Benzene > Pyridine.
Updated On: May 25, 2026
- Furan
- Thiophene
- Pyrrole
- Pyridine
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The Correct Option is C
Solution and Explanation
Step 1: Concept
Electrophilic aromatic substitution (EAS) reactivity in heterocycles depends on the electron density within the ring.
Step 2: Meaning
Five-membered heterocycles are "$\pi$-excessive" because 6 electrons are shared over 5 atoms, making them more reactive than benzene.
Step 3: Analysis
Nitrogen in Pyrrole is less electronegative than Oxygen (Furan) or Sulfur (Thiophene), making it better at donating its lone pair into the ring resonance. Pyridine is $\pi$-deficient and least reactive.
Step 4: Conclusion
Pyrrole has the highest electron density, making it the most reactive towards electrophiles. Final Answer: (C)
Electrophilic aromatic substitution (EAS) reactivity in heterocycles depends on the electron density within the ring.
Step 2: Meaning
Five-membered heterocycles are "$\pi$-excessive" because 6 electrons are shared over 5 atoms, making them more reactive than benzene.
Step 3: Analysis
Nitrogen in Pyrrole is less electronegative than Oxygen (Furan) or Sulfur (Thiophene), making it better at donating its lone pair into the ring resonance. Pyridine is $\pi$-deficient and least reactive.
Step 4: Conclusion
Pyrrole has the highest electron density, making it the most reactive towards electrophiles. Final Answer: (C)
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