Chemistry of Benzene:
Electrophilic Aromatic
Substitution
,Substitution Reactions of Benzene
and Its Derivatives
Benzene is aromatic: a cyclic conjugated compound with
6 electrons
Reactions of benzene lead to the retention of the aromatic
core
Electrophilic aromatic substitution replaces a proton on
benzene with another electrophile
2
,Bromination of Aromatic Rings
Benzene’s electrons participate as a Lewis base in reactions
with Lewis acids
The product is formed by loss of a proton, which is replaced by
bromine
FeBr3 is added as a catalyst to polarize the bromine reagent
3
, Addition Intermediate in
Bromination
The addition of bromine occurs in two steps
In the first step the electrons act as a nucleophile
toward Br2 (in a complex with FeBr3)
This forms a cationic addition intermediate from
benzene and a bromine cation
The intermediate is not aromatic and therefore high
in energy (see Figure 16.2)
4
Electrophilic Aromatic
Substitution
,Substitution Reactions of Benzene
and Its Derivatives
Benzene is aromatic: a cyclic conjugated compound with
6 electrons
Reactions of benzene lead to the retention of the aromatic
core
Electrophilic aromatic substitution replaces a proton on
benzene with another electrophile
2
,Bromination of Aromatic Rings
Benzene’s electrons participate as a Lewis base in reactions
with Lewis acids
The product is formed by loss of a proton, which is replaced by
bromine
FeBr3 is added as a catalyst to polarize the bromine reagent
3
, Addition Intermediate in
Bromination
The addition of bromine occurs in two steps
In the first step the electrons act as a nucleophile
toward Br2 (in a complex with FeBr3)
This forms a cationic addition intermediate from
benzene and a bromine cation
The intermediate is not aromatic and therefore high
in energy (see Figure 16.2)
4
