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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