Electrophilic reactions in aromatics

1. General Mechanism
Of Electrophilic aromatic
Substitution reaction
1

2.  Allows the formation of covalent bond
 Bond between aromatic cycle and electrophile
 By transferring on electron pair from aromatic compound.
 Two step mechanism:
Add of electrophile in the aromatic nucleus result in the formation of intermediate and called an arenium ion
2

3. 1.
2.
According to lewis concept Y is base because it donates electron
3

4. Sulphonation
 Sulphuric acid is incorporated in benzene ring by two method.
 Conc. Sulphuric acid at 80c
 Fuming Sulphuric acid at room temperature
4

5. 5

6. Desulphonation.
Or
protonation
6

7. 7
 When an aromatic sulfonic acid is heated to 100- 175c with aqueous acid.
 It is converted into sulfuric acid and an aromatic H/C.
 This desulfonation is the exact reverse of the sulfonation processed
by which the sulfuric acid was originally made.