Electrophilic Aromatic Substitution of Class 12

Most substitutions at an aliphatic carbon are nucleophilic. In aromatic systems the situation is reversed, because the high electron density at the aromatic ring attracts positive species and negative ones not so easily. In electrophilic substitutions the attacking species is a positive ion. The leaving group must necessarily depart without its electron pair, therefore in electrophilic substitutions the most important leaving groups are those that can best exist without the pair of electrons necessary to fill the outer shell, that is the weakest lewis acids. The most common leaving group in electrophilic aromatic substitutions is a proton. These reactions in the general form are shown below:

ArH + E+  →  Ar – E + H+

Electrophilic Aromatic Substitution

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