Electrophilic Substitution
3.3.10.2:
Electrophilic attack on benzene rings results in substitution, limited to
monosubstitutions
Nitration is an important step in synthesis, including the manufacture of explosives
and formation of amines
Friedel–Crafts acylation reactions are also important steps in synthesis
Students should be able to outline the electrophilic substitution mechanisms of:
nitration, including the generation of the nitronium ion
acylation using AlCl3 as a catalyst
Why does benzene not undergo addition reactions?
it would involve breaking up the delocalised pi-system
Outline a basic eletrophilic substitution mechanism
Which ion is used in the nitration of benzene?
NO2+
it does not exist
Electrophilic Substitution 1
, you must show how it is generated
How is this NO2+ ion generated? (reagents & equations)
Reagents: Concentrated H2SO4 (acts as a catalyst ∴ reforms at the end) &
concentrated HNO3
this mixture is called NITRATING MIXTURE
H2SO4 + HNO3 → H2NO3+ + HSO4-
H2NO3+ → H2O + NO2+
Overall: H2SO4 + HNO3 → HSO4- + NO2+ + H2O
How is the H2SO4 catalyst regenerated in the nitration of benzene?
HSO4- + H+ → H2SO4
(H+ from benzene ring)
Draw a mechanism and write an overall equation for the nitration of benzene
(include the conditions)
conditions: below 55*C, H2SO4 catalyst
otherwise multiple NO2+ will attack benzene resulting in multi-substitutions
Electrophilic Substitution 2
3.3.10.2:
Electrophilic attack on benzene rings results in substitution, limited to
monosubstitutions
Nitration is an important step in synthesis, including the manufacture of explosives
and formation of amines
Friedel–Crafts acylation reactions are also important steps in synthesis
Students should be able to outline the electrophilic substitution mechanisms of:
nitration, including the generation of the nitronium ion
acylation using AlCl3 as a catalyst
Why does benzene not undergo addition reactions?
it would involve breaking up the delocalised pi-system
Outline a basic eletrophilic substitution mechanism
Which ion is used in the nitration of benzene?
NO2+
it does not exist
Electrophilic Substitution 1
, you must show how it is generated
How is this NO2+ ion generated? (reagents & equations)
Reagents: Concentrated H2SO4 (acts as a catalyst ∴ reforms at the end) &
concentrated HNO3
this mixture is called NITRATING MIXTURE
H2SO4 + HNO3 → H2NO3+ + HSO4-
H2NO3+ → H2O + NO2+
Overall: H2SO4 + HNO3 → HSO4- + NO2+ + H2O
How is the H2SO4 catalyst regenerated in the nitration of benzene?
HSO4- + H+ → H2SO4
(H+ from benzene ring)
Draw a mechanism and write an overall equation for the nitration of benzene
(include the conditions)
conditions: below 55*C, H2SO4 catalyst
otherwise multiple NO2+ will attack benzene resulting in multi-substitutions
Electrophilic Substitution 2
