Electriphilic Substitution in Thiophene

Electrophilic Substitution of Thiophene

Thiophene undergoes electrophilic substitution reactions at position C-2.

i. Halogenation: Thiophene reacts with halogens [X2, Where X2= Cl2, Br2 And I2] to give 2-halothiophene. For example, the reaction of bromine with Thiophene in absence of any halogen carrier gives 2,5-dibenzothiophene.

However, the Iodination of thiophene in presence of yellow mercuric oxide gives 2-iodothiophene.

ii. Nitration: 2-Nitrothiophene is obtained when nitration of thiophene is performed by reacting it with fuming HNO3 in anhydride. The reaction of HNO3 and acetic anhydride resulted in acetyle nitrate in which -NO2 acts as an electrophile.

iii. Sulphonation: Sulphonation of thiophene is achieved by reacting it with cold concentrated H2SO4. Thiophene-2-sulphonic acid is obtained as a product.

iv. Friedel-Crafts Acylation: Reaction of thiophene with acetic anhydride in presence of H3PO4 gives 2-acetyl thiophene.

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