Chapter 22, Problem 22.66P

Interpretation Introduction

Interpretation:

A complete, detailed mechanism for the set of reactions shown is to be proposed.

Concept introduction:

Aromatic compounds undergo electrophilic aromatic substitution reactions. The reaction consists of electrophile addition-elimination. It starts with the aromatic compound using one of its $\text{π}$ electron pairs to form a bond to the electrophile. This produces an arenium cation. In the second step, a base, usually the counter ion of the electrophile, extract the proton from the carbon bonded to the electrophile. The $\text{C}-\text{H}$ bond pair moves to the positively charged ring carbon to reform the aromatic ring, producing the final product. The neutral compound is generally poor electrophiles and needs to be treated with a strong Lewis acid like ${\text{AlCl}}_{\text{3}}$ to increase their electrophilic character.