Chapter 15, Problem 15.64P

Devise a synthesis of each compound using ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms. You may use any other required organic or inorganic reagents.

a. $\text{HC}\equiv \text{CH}$ b. $\text{HC}\equiv {\text{CCH}}_{\text{2}}{\text{CH}}_{\text{3}}$ c. $\text{HC}\equiv {\text{CCH}}_{\text{2}}{\text{CH}}_{\text{3}}$ d. e.

Interpretation Introduction

(a)

Interpretation: The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms andby the use of any other organic or inorganic reagent is to be stated.

Concept introduction: Alkynes acts as a nucleophile by removing its terminal proton. This brings negative charge on terminal carbon atom. The negatively charged alkyne is known as acetylide anion.

Answer to Problem 15.64P

The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is,

Figure 1

Explanation of Solution

The synthesis of acetylene $\left(\text{HC}\equiv \text{CH}\right)$ starts from the bromination of ethane. The product obtained from this reaction is bromoethane. The product obtained from the reaction of bromoethane with potassium tert-butoxide undergoes addition reaction with ${\text{Br}}_{\text{2}}$ and leads to the formation of $1,2$-dibromoethane. The desired product acetylene is obtained by the reaction of $1,2$-dibromoethane with excess ${\text{NaNH}}_{\text{2}}$ as shown below.

Figure 1

Conclusion

The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is shown in Figure 1.

Interpretation Introduction

(b)

Interpretation: The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is to be stated.

Concept introduction: Alkynes acts as a nucleophile by removing its terminal proton. This brings negative charge on terminal carbon atom. The negatively charged alkyne is known as acetylide anion.

Answer to Problem 15.64P

The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is,

Explanation of Solution

The synthesis of acetylene $\left(\text{HC}\equiv \text{CH}\right)$ starts from the bromination of ethane. The product obtained from this reaction is bromoethane. The product obtained from the reaction of bromoethane with potassium tert-butoxide undergoes addition reaction with ${\text{Br}}_{\text{2}}$ and leads to the formation of $1,2$-dibromoethane. Acetylene is obtained by the reaction of $1,2$-dibromoethane with excess ${\text{NaNH}}_{\text{2}}$. In the last step, the desired product is obtained when ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{Br}$ is treated with acetylene in the presence of ${\text{NaNH}}_{\text{2}}$ as shown below.

Figure 2

Conclusion

The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is shown in Figure 2.

Interpretation Introduction

(c)

Interpretation: The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is to be stated.

Concept introduction: Alkynes acts as a nucleophile by removing its terminal proton. This brings negative charge on terminal carbon atom. The negatively charged alkyne is known as acetylide anion.

Answer to Problem 15.64P

The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is,

Explanation of Solution

The epoxidation of ethene, which is obtained from ethane, in the presence of m-chloroperbenzoic acid $\left(m\text{CPBA}\right)$ leads to the formation of oxirane as shown in Figure 3.

Figure 3

The synthesis of acetylene is shown in Figure 1. Acetylene undergoes nucleophilic substitution reaction with oxirane in the presence of base to yield desired product as shown in Figure 4.

Figure 4

Conclusion

The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is shown in Figure 3 and Figure 4.

Interpretation Introduction

(d)

Interpretation: The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is to be stated.

Concept introduction: Alkynes acts as a nucleophile by removing its terminal proton. This brings negative charge on terminal carbon atom. The negatively charged alkyne is known as acetylide anion.

Answer to Problem 15.64P

The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is,

Explanation of Solution

The synthesis of acetylene and bromoethane is shown in Figure 1. Acetylene undergoes nucleophilic substitution reaction with two molecules of bromoethane to form symmetrical alkyne. The triple bond of symmetrical alkyne is reduced to double bond on reaction with ${\text{Na/NH}}_{\text{3}}$ to give trans alkene as shown in Figure 5.

Figure 5

Conclusion

The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is shown in Figure 5.

Interpretation Introduction

(e)

Interpretation: The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is to be stated.

Concept introduction: Alkynes acts as a nucleophile by removing its terminal proton. This brings negative charge on terminal carbon atom. The negatively charged alkyne is known as acetylide anion.

Answer to Problem 15.64P

The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is,

Explanation of Solution

The synthesis of acetylene and bromoethane is shown in Figure 1. Acetylene undergoes nucleophilic substitution reaction with two molecules of bromoethane to form symmetrical alkyne. The symmetrical alkyne converts into ketone on reaction with ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}{\text{/H}}_{\text{2}}\text{O}$ as shown in Figure 6.

Figure 6

Conclusion

The synthesis of given compound from ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}$ as the only source of carbon atoms and by the use of any other organic or inorganic reagent is shown in Figure 6.