Electrophilic Aromatic Substitution Reaction

Electrophilic Aromatic Substitution Reaction

Contents

Electrophilic aromatic substitution

·        
Nitration

·        
Sulphonation

·        
Halogenation 

Nitration of Benzene 

•       A nitro group (-NO₂ )
substitutes for a hydrogen

•       Nitration of benzene with nitric
acid requires sulfuric acid as a catalyst

Mechanism

•       Step I  Generation of electrophile

•        Step 2 
Attack of electrophile leads to formation of sigma complex or wheland
complex which is resonance stabilized

•       Resonance stabilization of  wheland complex

•       Step 3  Loss of a proton gives nitrobenzene

Summary

•       Nitration is a electrophilic aromatic
substitution reaction

•       Nitro group is getting introduced in
benzene

•       Nitronium ion  acts as electrophile in nitration

•       Nitrating mixture is used for
nitration

•       Sulphur  trioxide is a neutral electrophile

•       Benzene on sulphonation gives
benzene sulphonic acid

•       For halogenation reaction ferric
bromide or ferric chloride is used

•       Ferric bromide or ferric
chloride  forms a complex with halogen

•       But it can act as nucleophile

•       Sulphonation leads to formation of
benzene sulphonic  acid

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