Waiting
Login processing...

Trial ends in Request Full Access Tell Your Colleague About Jove

18.9: Electrophilic Aromatic Substitution: Chlorination and Bromination of Benzene

TABLE OF
CONTENTS
JoVE Core
Organic Chemistry

A subscription to JoVE is required to view this content.

Education
Electrophilic Aromatic Substitution: Chlorination and Bromination of Benzene
 
TRANSCRIPT

18.9: Electrophilic Aromatic Substitution: Chlorination and Bromination of Benzene

Chlorination and bromination are important classes of electrophilic aromatic substitutions, where benzene reacts with chlorine or bromine in the presence of a Lewis acid catalyst to give halogenated substitution products. A Lewis acid such as aluminium chloride or ferric chloride catalyzes the chlorination, and ferric bromide catalyzes the bromination reactions. During the bromination of alkenes, bromine polarizes and becomes electrophilic. However, in the bromination of benzene, the bromine molecule reacts with ferric bromide by donating a pair of electrons to the Lewis acid, which creates a more polar Br–Br bond and forming a more reactive electrophile.

Figure1

The benzene attacks this electrophile to generate the arenium ion, which is resonance stabilized.

Figure2

A proton transfer from arenium ion forms bromobenzene, thereby restoring aromaticity and regenerating the catalyst.

Figure3

The mechanism of chlorination of benzene proceeds in the same manner as bromination of benzene.

Tags

Electrophilic Aromatic Substitution Chlorination Bromination Benzene Lewis Acid Catalyst Halogenated Substitution Products Aluminium Chloride Ferric Chloride Ferric Bromide Bromine Polarizes Electrophile Arenium Ion Resonance Stabilized Proton Transfer Bromobenzene

Get cutting-edge science videos from JoVE sent straight to your inbox every month.

Waiting X
Simple Hit Counter