Chapter 19, Problem 71PP

Interpretation Introduction

Interpretation:

The electrophilic aromatic substitution reaction of furan has to be explained.

Concept Introduction:

• Electrophiles are electron deficient species. In Electrophilic substitution reaction a group or atom in a compound is replaced by electrophile. This kind of reaction occurs predominantly in aromatic compounds. Electrophilic substitution reactions of aromatic compounds are known as aromatic electrophilic substitution reactions.

• The aromatic five-membered heterocycles all undergo electrophilic substitution, by means of a universal reactivity order: pyrrole >> furan > thiophene > benzene. The reaction situation proves plainly the better reactivity of furan compared with thiophene.
• While the electrophile attacks $\text{C-3}$ , together furan and pyrrole  intermediates will contain two significance structures, on the other hand, stipulation substitution is at the alpha position $\left(\text{C-2 or C-5}\right)$ reaction intermediates will have three significance structures.