Chapter 23, Problem 23.55P

Interpretation Introduction

(a)

Interpretation:

How to synthesize the given trisubstituted benzene from the disubstituted benzene is to be shown.

Concept introduction:

If multiple substituents are attached to a phenyl ring, their activating/deactivating qualities are additive, and the regiochemistry tends to be governed by the most activating of those substituents.

The alkyl group is ortho/para director whereas ${\text{NO}}_{\text{2}}$ group is meta director.

Answer to Problem 23.55P

The disubstituted benzene used to synthesize the given trisubstituted benzene is

Explanation of Solution

The given trisubstituted target molecule is

In the above molecule, ${\text{CH}}_{\text{3}}$ is an ortho/para director, and ${\text{NO}}_{\text{2}}$ is ortho to one ${\text{CH}}_{\text{3}}$ and para to another, that is, ${\text{NO}}_{\text{2}}$ group is added via electrophilic addition reaction.

This reaction can be carried out using addition of nitric acid ${\text{(NO}}_{\text{2}}{}^{+})$ to the disubstituted benzene with two alkyl group as substituents.

Therefore, the product could be produced by nitrating $\text{1, 3-dimethylbenzene}$:

Conclusion

The disubstituted benzene used to synthesize the given trisubstituted benzene is shown on the basis of the directing nature of the substituents present at the benzene ring on the target molecule (given trisubstituted benzene).

Interpretation Introduction

(b)

Interpretation:

How to synthesize the given trisubstituted benzene from the disubstituted benzene is to be shown.

Concept introduction:

If multiple substituents are attached to a phenyl ring, their activating/deactivating qualities are additive, and the regiochemistry tends to be governed by the most activating of those substituents.

Answer to Problem 23.55P

The disubstituted benzene used to synthesize the given trisubstituted benzene is

Explanation of Solution

The given trisubstituted target molecule is

In the above molecule, $\text{OH}$ is an ortho/para director, and ${\text{CH}}_{\text{3}}\text{C=O}$ is a meta director. The Cl is ortho to the $\text{OH}$ and meta to the ${\text{CH}}_{\text{3}}\text{C=O}$. Thus, the Cl group is added via electrophilic addition reaction.

Thus, the product could be produced by chlorinating the disubstituted benzene using ${\text{Cl}}_{\text{2}}{\text{/AlCl}}_{\text{3}}$ as shown below:

Conclusion

The disubstituted benzene used to synthesize the given trisubstituted benzene is shown on the basis of the directing nature of the substituents present at the benzene ring on the target molecule (given trisubstituted benzene).

Interpretation Introduction

(c)

Interpretation:

How to synthesize the given trisubstituted benzene from the disubstituted benzene is to be shown.

Concept introduction:

If multiple substituents are attached to a phenyl ring, their activating/deactivating qualities are additive, and the regiochemistry tends to be governed by the most activating of those substituents.

Answer to Problem 23.55P

The disubstituted benzene used to synthesize the given trisubstituted benzene is

Explanation of Solution

The given trisubstituted target molecule is

In the above molecule, ${\text{CH}}_{\text{3}}$ is an ortho/para director (activator), and ${\text{NO}}_{\text{2}}$ is a meta director (deactivator). The ${\text{SO}}_{\text{3}}\text{H}$ substituent is ortho to the ${\text{CH}}_{\text{3}}$ and para to the ${\text{NO}}_{\text{2}}$. These groups are in disagreement, but the ${\text{CH}}_{\text{3}}$ group-activator directs the regiochemistry.

Therefore, the product could be produced by sulfonating the disubstituted benzene using fuming ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$, which is added to the deactivated disubstituted benzene with ${\text{CH}}_{\text{3}}{\text{ and NO}}_{\text{2}}$, as shown below:

Conclusion

The disubstituted benzene used to synthesize the given trisubstituted benzene is shown on the basis of the directing nature of the substituents present at the benzene ring on the target molecule (given trisubstituted benzene).

Interpretation Introduction

(d)

Interpretation:

How to synthesize the given trisubstituted benzene from the disubstituted benzene is to be shown.

Concept introduction:

If multiple substituents are attached to a phenyl ring, their activating/deactivating qualities are additive, and the regiochemistry tends to be governed by the most activating of those substituents.

Answer to Problem 23.55P

The disubstituted benzene used to synthesize the given trisubstituted benzene is

Explanation of Solution

The given trisubstituted target molecule is

Here, both ${\text{Cl and CH}}_{\text{3}}\text{O}$ are ortho/para directors. The Br is ortho to the Cl and para to the ${\text{CH}}_{\text{3}}\text{O}$. Thus, the Br atom is added via electrophilic substitution reaction to the disubstituted benzene with ${\text{Cl and CH}}_{\text{3}}\text{O}$ groups as two substituents.

Therefore, the target molecule could be produced by brominating the disubstituted benzene using ${\text{Br}}_{\text{2}}{\text{/FeBr}}_{\text{3}}$, as shown below:

Conclusion

The disubstituted benzene used to synthesize the given trisubstituted benzene is shown on the basis of the directing nature of the substituents present at the benzene ring on the target molecule (given trisubstituted benzene).