Subject: Organic Chemistry · Chapter: General Organic Chemistry · Topic: Aromaticity · Exam: CSIR-NET JUNE 2011 · Marks: 2 · Difficulty: Hard
With respect to electrophilic aromatic substitution, reactivity order of pyrrole, pyridine and indole is
(a)indole > pyrrole > pyridine
(b)pyrrole > pyridine > indole
(c)pyrrole > indole > pyridine
(d)indole > pyridine > pyrrole
Answer
Answer (as printed): C
Explanation
• Pyrrole is π-rich centre. The HOMO of pyrrole is at high energy level thus making it more reactive towards electrophilic aromatic substitution. • Pyridine is π-sink centre. The HOMO of pyridine is at low energy level and gives nucleophilic substitution reaction than electrophilic substitution reaction.
Explanation as extracted from the printed page; notation may be imperfect.