Chapter 7, Problem 7.69P

Interpretation Introduction

(a)

Interpretation: The mechanism of given nucleophilic substitution reaction is to be determined and the products, along with their stereochemistry, are to be drawn.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. The electron rich chemical species that contains negative charge or lone pair of electrons are known as a nucleophile. In a nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking the electron deficient carbon atom.

Answer to Problem 7.69P

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{2}$. The products of the reaction are shown in Figure 1.

Explanation of Solution

The structure of the given alkyl halide shows that a carbon atom, on which bromine is present, is bonded to one another carbon atom. Hence, the bromine atom is bonded to primary carbon atom and the given alkyl halide is $1°$. The primary alkyl halide is most likely to undergo nucleophilic substitution reaction through ${\text{S}}_{\text{N}}\text{2}$ mechanism.

In ${\text{S}}_{\text{N}}\text{2}$ mechanism, the removal of halide and the attack of nucleophile take place simultaneously in the transition state. The incoming nucleophile attacks from the back side on the carbon atom from which halide group is leaving. As a result, the inversion of configuration takes place.

However, in the given reaction halogen atom is not attached to chiral carbon. It is bonded to non-chiral carbon atom. The attack of nucleophile has not affect on the stereochemistry of reactant as shown in Figure 1.

Figure 1

The stereochemistry of reactant and product is same.

Conclusion

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{2}$. The products of the reaction are shown in Figure 1.

Interpretation Introduction

(b)

Interpretation: The mechanism of given nucleophilic substitution reaction is to be determined and the products, along with their stereochemistry, are to be drawn.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. The electron rich chemical species that contains negative charge or lone pair of electrons are known as a nucleophile. In a nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking the electron deficient carbon atom.

Answer to Problem 7.69P

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{2}$. The products of the reaction are shown in Figure 2.

Explanation of Solution

The structure of the given alkyl halide shows that a carbon atom, on which bromine atom is present, is bonded to two other carbon atoms. Hence, the bromine atom is bonded to secondary carbon atom. The removal of bromine atom leads to the formation of secondary carbocation. The secondary carbocation can undergo nucleophilic substitution reaction through both ${\text{S}}_{\text{N}}\text{1}$ and ${\text{S}}_{\text{N}}\text{2}$ mechanism. However, a secondary carbocation undergo nucleophilic substitution reaction through ${\text{S}}_{\text{N}}\text{2}$ mechanism on reaction with strong nucleophile. In the given reaction, ${\text{CH}}_{\text{3}}{\text{O}}^{-}$ is a strong nucleophile.

In ${\text{S}}_{\text{N}}\text{2}$ mechanism, the incoming nucleophile attacks from the back side on the carbon atom from which halide group is leaving. As a result, the inversion of configuration takes place. The product of the given reaction is shown in Figure 2.

Figure 2

Conclusion

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{2}$. The products of the reaction are shown in Figure 2.

Interpretation Introduction

(c)

Interpretation: The mechanism of given nucleophilic substitution reaction is to be determined and the products, along with their stereochemistry, are to be drawn.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. The electron rich chemical species that contains negative charge or lone pair of electrons are known as a nucleophile. In a nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking the electron deficient carbon atom.

Answer to Problem 7.69P

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{1}$. The products of the reaction are shown in Figure 3.

Explanation of Solution

The structure of the given alkyl halide shows that carbon atom, on which bromine atom is present, is bonded to three other carbon atoms. Hence, the bromine atom is bonded to tertiary carbon atom. The removal of bromine atom leads to the formation of planer tertiary carbocation. The tertiary carbocation is most likely to undergo nucleophilic substitution reaction by ${\text{S}}_{\text{N}}\text{1}$ mechanism because tertiary carbocation is most stable.

In ${\text{S}}_{\text{N}}\text{1}$ reaction, two products are obtained that have different stereochemistry. They are formed by the attack of nucleophile below and above the plane of planer tertiary carbocation. The product obtained by the given reaction is shown in Figure 3.

Figure 3

Conclusion

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{1}$. The products of the reaction are shown in Figure 3.

Interpretation Introduction

(d)

Interpretation: The mechanism of given nucleophilic substitution reaction is to be determined and the products, along with their stereochemistry, are to be drawn.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. The electron rich chemical species that contains negative charge or lone pair of electrons are known as a nucleophile. In a nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking the electron deficient carbon atom.

Answer to Problem 7.69P

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{1}$. The products of the reaction are shown in Figure 4.

Explanation of Solution

The structure of the given alkyl halide shows that a carbon atom, on which iodine atom is present, is bonded to two other carbon atoms. Hence, the iodine atom is bonded to secondary carbon atom. The removal of iodine atom leads to the formation of secondary carbocation. The secondary carbocation can undergo nucleophilic substitution reaction through both ${\text{S}}_{\text{N}}\text{1}$ and ${\text{S}}_{\text{N}}\text{2}$ mechanism. However, a secondary carbocation undergo nucleophilic substitution reaction through ${\text{S}}_{\text{N}}\text{1}$ mechanism on reaction with weak nucleophile. In the given reaction, ${\text{CH}}_{\text{3}}{\text{CO}}_2\text{H}$ is a weak nucleophile.

In ${\text{S}}_{\text{N}}\text{1}$ reaction, two products are obtained that have different stereochemistry. They are formed by the attack of nucleophile below and above the plane of planer tertiary carbocation. The product obtained by the given reaction is shown in Figure 4.

Figure 4

Conclusion

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{1}$. The products of the reaction are shown in Figure 4.

Interpretation Introduction

(e)

Interpretation: The mechanism of given nucleophilic substitution reaction is to be determined and the products, along with their stereochemistry, are to be drawn.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. The electron rich chemical species that contains negative charge or lone pair of electrons are known as a nucleophile. In a nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking the electron deficient carbon atom.

Answer to Problem 7.69P

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{2}$. The products of the reaction are shown in Figure 5.

Explanation of Solution

The structure of the given alkyl halide shows that a carbon atom, on which bromine atom is present, is bonded to two other carbon atoms. Hence, the bromine atom is bonded to secondary carbon atom. The removal of bromine atom leads to the formation of secondary carbocation. The secondary carbocation can undergo nucleophilic substitution reaction through both ${\text{S}}_{\text{N}}\text{1}$ and ${\text{S}}_{\text{N}}\text{2}$ mechanism. However, a secondary carbocation undergo nucleophilic substitution reaction through ${\text{S}}_{\text{N}}\text{2}$ mechanism on reaction with strong nucleophile. In the given reaction, ${\text{CH}}_{\text{3}}{\text{CH}}_2{\text{O}}^{-}$ is a strong nucleophile.

In ${\text{S}}_{\text{N}}\text{2}$ mechanism, the incoming nucleophile attacks from the back side on the carbon atom from which halide group is leaving. As a result, the inversion of configuration takes place. The product of the given reaction is shown in Figure 5.

Figure 5

Conclusion

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{2}$. The products of the reaction are shown in Figure 5.

Interpretation Introduction

(f)

Interpretation: The mechanism of given nucleophilic substitution reaction is to be determined and the products, along with their stereochemistry, are to be drawn.

Concept introduction: The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as substitution reaction. The electron rich chemical species that contains negative charge or lone pair of electrons are known as a nucleophile. In a nucleophilic substitution reaction, nucleophile takes the position of leaving group by attacking the electron deficient carbon atom.

Answer to Problem 7.69P

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{1}$. The products of the reaction are shown in Figure 6.

Explanation of Solution

The structure of the given alkyl halide shows that a carbon atom, on which bromine atom is present, is bonded to two other carbon atoms. Hence, the bromine atom is bonded to secondary carbon atom. The removal of bromine atom leads to the formation of secondary carbocation. The secondary carbocation can undergo nucleophilic substitution reaction through both ${\text{S}}_{\text{N}}\text{1}$ and ${\text{S}}_{\text{N}}\text{2}$ mechanism. However, a secondary carbocation undergo nucleophilic substitution reaction through ${\text{S}}_{\text{N}}\text{1}$ mechanism on reaction with weak nucleophile. In the given reaction, ${\text{CH}}_{\text{3}}{\text{CH}}_2\text{OH}$ is a weak nucleophile.

In ${\text{S}}_{\text{N}}\text{1}$ reaction, two products are obtained that have different stereochemistry. They are formed by the attack of nucleophile below and above the plane of planer tertiary carbocation. The product obtained by the given reaction is shown in Figure 6.

Figure 6

Conclusion

The mechanism of given nucleophilic substitution reaction is ${\text{S}}_{\text{N}}\text{1}$. The products of the reaction are shown in Figure 6.