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ELECTROPHILIC AROMATIC SUBSTITUION REACTION
OF BENZENE
Definition:
Electrophilic aromatic substitution reactions are organic reactions where an
electrophile replaces an atom which is attached to an aromatic ring
...

The aromaticity of the aromatic system is preserved in an electrophilic
aromatic substitution reaction
...

There are many types of electrophilic aromatic substitution reactions, the most
important of which include:
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Aromatic nitration reactions
Electrophilic aromatic halogenation reactions
Aromatic sulfonation reactions
Friedel-Crafts alkylation reaction
Friedel-Crafts acylation reaction

AROMATIC NITRATION REACTION
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Nitration reaction involves the replacement of a hydrogen with a nitro (NO2)
group
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The key to the process is protonation of OH on nitric acid, which
converts it to H2O
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The nitronium ion formed in the first step acts as an electrophile and attacks
the benzene to give benzenium ion or arenium ion
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AROMATIC SULFONATION REACTION
Aromatic sulfonation is an organic reaction in which a hydrogen atom
on an arene is replaced by a sulfonic acid functional group

Step 1:

Sulfur trioxide is “activated” by the addition of a proton from sulfuric
acid
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The HSO4– ion left after protonation of SO3 removes a proton from
carbon bearing sulfonic group and yield benzene sulfonic acid
AROMATIC HALOGENATION REACTION
Benzene can be halogenated with chlorine and bromine in the presence of
lewis acid such as FeCl3 and AlCl3,
which assist in the polarization of
halogen molecules making it more
reactive
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Iodine is unreactive even in
the presence of catalyst
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The FeCl
is then free to react with another equivalent of Cl
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Attack of the activated electrophile by the aromatic ring
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Deprotonation to regenerate the aromatic ring
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This
electrophilic aromatic substitution reaction is known as the Friedel-Crafts
alkylation reaction
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This electrophilic substitution
reaction is known as Friedel craft acylation

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