Chapter 23, Problem 23.1P

Interpretation Introduction

(a)

Interpretation:

The major product for the given reaction is to be predicted, and the complete, detailed mechanism for the same reaction is to be drawn.

Concept introduction:

In the case of an electrophilic aromatic substitution reaction, a substituent influences the site of reaction. The electron-donating groups are ortho/para directing groups while electron-withdrawing groups are meta directing groups in the electrophilic aromatic substitution reaction. The Friedel-Crafts alkylation and acylation are an example of an electrophilic aromatic substitution reaction. The chlorination of the aromatic ring can be carried out by reacting with ${\text{Cl}}_2$ in the presence of ${\text{FeCl}}_{\text{3}}$, which is also an example of an electrophilic aromatic substitution reaction. In Friedel-Crafts reaction, the first step is the formation of an electrophile, and then the electrophilic addition-elimination takes place with the aromatic ring and the electrophile.

Answer to Problem 23.1P

The major product for the given reaction is

The complete, detailed mechanism for the given reaction is given below.

Formation of the electrophile:

Formation of the product (a racemic mixture of ortho and para isomer):

For ortho isomer:

For para isomer:

Explanation of Solution

The given reaction is

It is noticed that the given substrate, phenol, is treated with ethyl chloride in the presence of ${\text{AlCl}}_{\text{3}}$ as a catalyst. So it is an example of the Friedel-Crafts alkylation reaction. Since the electron-donating $\text{OH}$ group is directly attached to the benzene ring, which is ortho/para director in electrophilic aromatic substitution, the reaction leads to giving the racemic mixture of the product. Therefore, the products of the given reaction are

The mechanism for the given reaction is given below.

Since the given reaction is an example of an electrophilic aromatic substitution reaction, the first step is the formation of the electrophile as given below.

Initially, the electron-rich chlorine of the ethyl chloride is coordinated with an electron-deficient aluminum of ${\text{AlCl}}_{\text{3}}$ followed by heterolysis of $\text{C-Cl}$ bond to form the corresponding ethyl cation, which is nothing but the required electrophile.

The formed electrophile, ethyl cation (${\text{CH}}_{\text{3}}{\text{-CH}}_{\text{2}}{}^{\text{+}}$), then underdoes electrophilic addition to the benzene ring, followed by electrophilic elimination mechanism to form the ortho and para isomers shown below:

For ortho isomer:

For para isomer:

Conclusion

The major product for the given reaction is predicted, and the complete, detailed mechanism for the same reaction is drawn on the basis of the electrophilic aromatic substitution reaction.

Interpretation Introduction

(b)

Interpretation:

The major product for the given reaction is to be predicted, and the complete, detailed mechanism for the same reaction is to be drawn.

Concept introduction:

In the case of an electrophilic aromatic substitution reaction, a substituent influences the site of reaction. The electron-donating groups are ortho/para directing groups while electron-withdrawing groups are meta directing groups in the electrophilic aromatic substitution reaction. The Friedel-Crafts alkylation and acylation are an example of an electrophilic aromatic substitution reaction. The chlorination of the aromatic ring can be carried out by reacting with ${\text{Cl}}_2$ in the presence of ${\text{FeCl}}_{\text{3}}$, which is also an example of an electrophilic aromatic substitution reaction. In Friedel-Crafts reaction, the first step is the formation of an electrophile, and then the electrophilic addition-elimination takes place with the aromatic ring and the electrophile.

Answer to Problem 23.1P

The major product for the given reaction is

The complete, detailed mechanism for the given reaction is given below.

Formation of the electrophile:

Formation of the product:

Explanation of Solution

The given reaction is

It is noticed that the given substrate is treated with ${\text{Cl}}_2$ in the presence of ${\text{FeCl}}_{\text{3}}$; it is an example of electrophilic aromatic substitution reaction. Since the nitro group is a meta director, the major product of the given reaction is m-chloronitrobenzene.

The mechanism for the given reaction is given below.

Since the given reaction is an example of an electrophilic aromatic substitution reaction, the first step is the formation of the electrophile as given below.

Initially, one of the electron-rich chlorine atoms of ${\text{Cl}}_2$ is coordinated with an electron-deficient iron metal of ${\text{FeCl}}_{\text{3}}$, followed by heterolysis of $\text{Cl-Cl}$ bond to form the corresponding cation, which is nothing but the required electrophile.

The formed electrophile (${\text{Cl}}^{\text{+}}$) then underdoes electrophilic addition to the benzene ring, followed by electrophilic elimination mechanism, to form the major meta isomer as the product, as shown below:

Conclusion

The major product for the given reaction is predicted, and the complete, detailed mechanism for the same reaction is drawn on the basis of the electrophilic aromatic substitution reaction.

Interpretation Introduction

(c)

Interpretation:

The major product for the given reaction is to be predicted, and the complete, detailed mechanism for the same reaction is to be drawn.

Concept introduction:

In the case of an electrophilic aromatic substitution reaction, a substituent influences the site of reaction. The electron-donating groups are ortho/para directing groups while electron-withdrawing groups are meta directing groups in the electrophilic aromatic substitution reaction. The Friedel-Crafts alkylation and acylation are an example of an electrophilic aromatic substitution reaction. The chlorination of the aromatic ring can be carried out by reacting with ${\text{Cl}}_2$ in the presence of ${\text{FeCl}}_{\text{3}}$, which is also an example of an electrophilic aromatic substitution reaction. In Friedel-Crafts reaction, the first step is the formation of an electrophile, and then the electrophilic addition-elimination takes place with the aromatic ring and the electrophile.

Answer to Problem 23.1P

The major product for the given reaction is

The complete, detailed mechanism for the given reaction is given below.

Formation of the electrophile:

Formation of the product (a racemic mixture of ortho and para isomer):

For ortho isomer:

For para isomer:

Explanation of Solution

The given reaction is

It is noticed that the given substrate, toluene, is treated with an acyl chloride in the presence of ${\text{AlCl}}_{\text{3}}$ as a catalyst. So it is an example of Friedel-Crafts acylation reaction. Since the electron-donating ${\text{CH}}_{\text{3}}$ group is directly attached to the benzene ring, which is ortho/para director in electrophilic aromatic substitution reaction, it leads to giving the mixture of the products. Therefore, the products of the given reaction are

From the Table 23-1, the product is a mixture of o+p isomer more than 95%.

The mechanism for the given reaction is given below.

Since the given reaction is an example of electrophilic aromatic substitution reaction, the first step is the formation of the electrophile as given below.

Initially, electron-rich chlorine of the ethyl chloride is coordinated with an electron-deficient aluminum of ${\text{AlCl}}_{\text{3}}$, followed by heterolysis of $\text{C-Cl}$ bond to form the corresponding acylium cation, which is nothing but the required electrophile.

The formed electrophile, acylium cation, then undergoes electrophilic addition to the benzene ring, followed by electrophilic elimination mechanism, to form the ortho and para isomers shown below:

For ortho isomer:

For para isomer:

Conclusion

The major product for the given reaction is predicted, and the complete, detailed mechanism for the same reaction is drawn on the basis of the electrophilic aromatic substitution reaction.

Interpretation Introduction

(d)

Interpretation:

The major product for the given reaction is to be predicted, and the complete, detailed mechanism for the same reaction is to be drawn.

Concept introduction:

In the case of an electrophilic aromatic substitution reaction, a substituent influences the site of reaction. The electron-donating groups are ortho/para directing groups while electron-withdrawing groups are meta directing groups in the electrophilic aromatic substitution reaction. The Friedel-Crafts alkylation and acylation are an example of an electrophilic aromatic substitution reaction. The chlorination of the aromatic ring can be carried out by reacting with ${\text{Cl}}_2$ in the presence of ${\text{FeCl}}_{\text{3}}$, which is also an example of an electrophilic aromatic substitution reaction. In Friedel-Crafts reaction, the first step is the formation of an electrophile, and then the electrophilic addition-elimination takes place with the aromatic ring and the electrophile.

Answer to Problem 23.1P

The major product for the given reaction is

The complete, detailed mechanism for the given reaction is given below.

Formation of the electrophile:

Formation of the product:

Explanation of Solution

The given reaction is

It is noticed that the given substrate is treated with ${\text{Br}}_{\text{2}}$ in the presence of ${\text{FeBr}}_{\text{3}}$; it is an example of an electrophilic aromatic substitution reaction. Since the acyl group is a meta director, the major product of the given reaction is $\text{m-bromoacetophenone}$.

The mechanism for the given reaction is given below.

Since the given reaction is an example of an electrophilic aromatic substitution reaction, the first step is the formation of the electrophile as given below.

Initially, one of the electron-rich bromine atoms of ${\text{Br}}_{\text{2}}$ is coordinated with an electron-deficient iron metal of ${\text{FeBr}}_{\text{3}}$ followed by heterolysis of $\text{Br-Br}$ bond, to form the corresponding cation, which is nothing but the required electrophile.

The formed electrophile (${\text{Br}}^{\text{+}}$) then undergoes electrophilic addition to the benzene ring, followed by electrophilic elimination mechanism, to form the major meta isomer as the product, as shown below:

Conclusion

The major product for the given reaction is predicted, and the complete, detailed mechanism for the same reaction is drawn on the basis of the electrophilic aromatic substitution reaction.