Chapter 23, Problem 23.85P

Interpretation Introduction

(a)

Interpretation:

Synthesis of the given compound from benzene is to shown.

Concept introduction:

The ${\text{CH}}_{\text{3}}$ group is added to the $\text{benzene}$ ring via Friedal-crafts acylation by using $\text{C}\equiv \text{O/HCl}$, followed by a reduction of the $\text{HC=O}$ to ${\text{CH}}_{\text{3}}$. Fuming sulfuric acid is then added to the ring to sulfonate the para position. This blocks the para position and allows addition of two $\text{Cl}$ +groups ortho to the ${\text{CH}}_{\text{3}}$ in the presence of excess of ${\text{Cl}}_{\text{2}}{\text{/AlCl}}_{\text{3}}$. The $\text{SO}\text{H}$ is then removed to yield the target compound.

Interpretation Introduction

(b)

Interpretation:

Synthesis of the given compound from benzene is to shown.

Concept introduction:

The ${\text{NH}}_{\text{2}}$ group on the ring directs an acyl group para in a Friedal-Crafts acylation, which can then be reduced to convert it to the alkyl group. The ${\text{NH}}_{\text{2}}$ group can come from nitration of benzene, followed by reduction of the ${\text{NO}}_{\text{2}}$. However, we must protect the ${\text{NH}}_{\text{2}}$ group before the introduction of the strong Lewis acid. Otherwise, the Lewis acid will complex to the ${\text{NH}}_{\text{2}}$ group, turning it into a strong deactivating group. This would prevent the necessary Fridal-Crafts reactions from happening. We protect the ${\text{NH}}_{\text{2}}$ group by using acetic anhydride and deprotect it in the final step using hydrolysis under basic conditions.