2. Compare the pka of pyrrole and imidazole. Which heterocycle is more basic? Applying the Hückel rule of aromaticity, can you explain this difference in reactivity? Protonated pyrrole (2): pka = -3.8 H H + H* H- H `H 1 2 Protonated imidazole (4): pKa = 7.0 H H -N: + H* H H- 4

2. Compare the pka of pyrrole and imidazole. Which heterocycle is more basic? Applying the Hückel rule of aromaticity, can you explain this difference in reactivity? Protonated pyrrole (2): pka = -3.8 H H + H* H- H `H 1 2 Protonated imidazole (4): pKa = 7.0 H H -N: + H* H H- 4

Organic Chemistry: A Guided Inquiry

2nd Edition

ISBN:9780618974122

Author:Andrei Straumanis

Publisher:Andrei Straumanis

Chapter19: Eas: Electrophilic Aromatic Substitution

Section: Chapter Questions

Problem 17E

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Question

Solve Question 2 with detailed explanation

2. Compare the pKa of pyrrole and imidazole. Which heterocycle is more basic? Applying the
Hückel rule of aromaticity, can you explain this difference in reactivity?
Protonated pyrrole (2): pka = -3.8
H
H
H
+ H*
H-
H-
H `H
1
Protonated imidazole (4): pKa = 7.0
H
H
-N:
+ H*
H
::
-H
3
4

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