University:
Alliant International University
Course:
BIO15000 | Introduction to General, Organic, and Biological Chemistry
Academic year:

2022
Views:

128

Pages:

4
Author:

kundgetanufv

Electrophilic Aromatic Substitution Reactions The most common reaction of aromatic compounds is electrophilic aromatic substitution, a process in which an electrophile (E) reacts with an aromatic ring and substitutes for one of the hydrogens. Many different substituents can be introduced onto the aromatic ring by electrophilic substitution. • To list some possibilities, an aromatic ring can be substituted by a halogen ( Cl, -Br, -I), a nitro group ( -NO2), a sulfonic acid group ( -SO3H), an alkyl group (R), or an acyl group ( -COR). • Starting from only a few simple materials, it’s possible to prepare many thousands of substituted aromatic compounds (Figure 5.2). Mechanism of Electrophilic Aromatic Substitution Bromination of Benzene • Bromine does not react with benzene at room temperature. • For bromination of benzene to take place, a catalyst such as FeBr3 is needed. • The catalyst makes the Br2 molecule more electrophilic by reacting with it to give FeBr4- and Br+. • The electrophilic Br+ then reacts with the electron-rich (nucleophilic) benzene ring • to yield a carbocation intermediate that is not aromatic. This carbocation is doubly allylic and is a hybrid of three resonance forms