Chapter 16, Problem 16.35AP

Interpretation Introduction

(a)

Interpretation:

The product for the reaction of ethylbenzene with bromine gas and ${\text{CCl}}_{\text{4}}$ in dark is to be predicted.

Concept introduction:

An electrophilic aromatic substitution reaction is a type of reaction in which an electrophile substitutes a hydrogen atom of the aromatic ring. Aromatic ring does not easily undergo nucleophilic substitution reaction; however, it undergoes electrophilic substitution reaction easily.

Answer to Problem 16.35AP

No product will be formed in the reaction of ethylbenzene with bromine gas and ${\text{CCl}}_{\text{4}}$ in dark.

Explanation of Solution

Ethylbenzene is ortho and para directing group, the electrophile will substitute on either ortho or para position of the benzene ring. In the dark no bromine free radical will be generated, therefore, no free radical reaction will occur. Carbon tetrachloride does not facilitate the production of positively charged ${\text{Br}}^{+}$ ion. Therefore, no electrophilic aromatic substitution reaction will take place between ethylbenzene and bromine gas.

Conclusion

No reaction takes place between ethylbenzene with bromine gas and ${\text{CCl}}_{\text{4}}$ in dark.

Interpretation Introduction

(b)

Interpretation:

The product for the reaction ethylbenzene with ${\text{HNO}}_{\text{3}}$ and ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ is to be predicted.

Concept introduction:

An electrophilic aromatic substitution reaction is a type of reaction in which an electrophile substitutes a hydrogen atom of the aromatic ring. Aromatic ring does not easily undergo nucleophilic substitution reaction; however, it undergoes electrophilic substitution reaction easily.

Answer to Problem 16.35AP

The products for the reaction ethylbenzene with ${\text{HNO}}_{\text{3}}$ and ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ are shown below.

Explanation of Solution

Ethylbenzene is ortho and para directing group, the electrophile will substitute on either ortho or para position of the benzene ring. The nitronium ion $\left({\text{NO}}_{\text{2}}{}^{+}\right)$ is generated from nitric acid by the help of sulphuric acid. The nitronium ion gets substituted either ortho or para position of ethylbenzene.

The corresponding chemical reaction is shown below.

Figure 1

Conclusion

The products for the reaction ethylbenzene with ${\text{HNO}}_{\text{3}}$ and ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ are shown Figure 1.

Interpretation Introduction

(c)

Interpretation:

The product for the reaction ethylbenzene with concentrated ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ is to be predicted.

Concept introduction:

An electrophilic aromatic substitution reaction is a type of reaction in which an electrophile substitutes a hydrogen atom of the aromatic ring. Aromatic ring does not easily undergo nucleophilic substitution reaction; however, it undergoes electrophilic substitution reaction easily.

Answer to Problem 16.35AP

The products for the reaction ethylbenzene with concentrated ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ are shown below.

Explanation of Solution

Ethylbenzene is ortho and para directing group, the electrophile will substitute on either ortho or para position of the benzene ring. In the presence of concentrated sulphuric acid, the $-{\text{SO}}_{\text{3}}\text{H}$ attacks either ortho or para position of ethylbenzene to form the product. The corresponding chemical reaction is shown below.

Figure 2

Conclusion

The products for the reaction ethylbenzene with concentrated ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ are shown in Figure 2.

Interpretation Introduction

(d)

Interpretation:

The product for the reaction ethylbenzene with propionyl chloride and ${\text{AlCl}}_{\text{3}}\left(1.1\text{ equiv}\text{.}\right)$, then with water is to be predicted.

Concept introduction:

Friedel Craft acylation is an electrophilic aromatic substitution reaction. In this reaction, the synthesis of the monoacylated product takes place from the reaction between aromatic rings and acyl chlorides.

Answer to Problem 16.35AP

The products for the reaction of ethylbenzene with propionyl chloride and ${\text{AlCl}}_{\text{3}}\left(1.1\text{ equiv}\text{.}\right)$, then with water are shown below.

Explanation of Solution

Friedel-Crafts alkylation permits the synthesis of alkylated products by the reaction of arenes with alkyl chlorides in the presence of aluminum chloride (Lewis acid). This alkylation reaction comes under the category of electrophilic aromatic substitution. Ethylbenzene is ortho and para directing group, the electrophile will substitute on either ortho or para position of the benzene ring. The acyl group attacks either ortho or para position of ethylbenzene to form the product. The corresponding chemical reaction is shown below.

Figure 3

Conclusion

The products for the reaction ethylbenzene with propionyl chloride and ${\text{AlCl}}_{\text{3}}\left(1.1\text{ equiv}\text{.}\right)$, then with water are shown in Figure 3.

Interpretation Introduction

(e)

Interpretation:

The product for the exothermic reaction of ethylbenzene with ${\text{CH}}_{\text{3}}\text{Br}$ and ${\text{AlCl}}_{\text{3}}$ is to be predicted.

Concept introduction:

An electrophilic aromatic substitution reaction is a type of reaction in which an electrophile substitutes a hydrogen atom of the aromatic ring. Aromatic ring does not easily undergo nucleophilic substitution reaction; however, it undergoes electrophilic substitution reaction easily.

Answer to Problem 16.35AP

The product for the exothermic reaction of ethylbenzene with ${\text{CH}}_{\text{3}}\text{Br}$ and ${\text{AlCl}}_{\text{3}}$ is shown below.

Explanation of Solution

Ethylbenzene is ortho and para directing group, the electrophile will substitute on either ortho or para position of the benzene ring. In the presence of ${\text{AlCl}}_{\text{3}}$ catalyst, ${\text{CH}}_{\text{3}}{}^{+}$ group is generated which attacks either ortho or para position of ethylbenzene to form the product. The corresponding chemical reaction is shown below.

Figure 4

Conclusion

The product for the exothermic reaction of ethylbenzene with ${\text{CH}}_{\text{3}}\text{Br}$ and ${\text{AlCl}}_{\text{3}}$ is shown in Figure 4.

Interpretation Introduction

(f)

Interpretation:

The product for the exothermic reaction of ethylbenzene with bromine gas and ${\text{FeBr}}_{\text{3}}$ is to be predicted.

Concept introduction:

An electrophilic aromatic substitution reaction is a type of reaction in which an electrophile substitutes a hydrogen atom of the aromatic ring. Aromatic ring does not easily undergo nucleophilic substitution reaction; however, it undergoes electrophilic substitution reaction easily.

Answer to Problem 16.35AP

The products for the exothermic reaction of ethylbenzene with bromine gas and ${\text{FeBr}}_{\text{3}}$ are shown below.

Explanation of Solution

Ethylbenzene is ortho and para directing group, the electrophile will substitute on either ortho or para position of the benzene ring. In this reaction, positively charged ${\text{Br}}^{+}$ ion is generated with the help of ${\text{FeBr}}_{\text{3}}$ catalyst. The ion ${\text{Br}}^{+}$ attacks either ortho or para position of ethylbenzene to form product. The corresponding chemical reaction is shown below.

Figure 5

Conclusion

The products for the exothermic reaction ethylbenzene with bromine gas and ${\text{FeBr}}_{\text{3}}$ are shown in Figure 5.