Chapter 17, Problem 17.24P

Interpretation Introduction

(a)

Interpretation:

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

Concept introduction:

The addition reaction mechanism dominates on whether the nucleophile adds to the carbonyl carbon reversibly or irreversibly. Nucleophilic addition is irreversible or reversible depends on charge stability. Nucleophilic addition tends to be irreversible if the negative charge that develops in the adduct is substantially better stabilized than it is in the nucleophile. Nucleophilic addition to a carbonyl carbon tends to be irreversible when it involves a very strong nucleophile like ${\text{R}}^{\text{-}}$ and ${\text{H}}^{\text{-}}$. Otherwise, the nucleophile addition tends to be reversible. In $\text{α,β}$ unsaturated carbonyl undergoes nucleophilic addition, Nucleophile that add reversibly to the carbonyl carbon yields the conjugate addition product as the major product and nucleophile that add irreversibly to the carbonyl carbon yield the direct addition product as the major product.

Answer to Problem 17.24P

The major product and mechanism for the given reaction are:

Explanation of Solution

The nucleophile ${\text{CH}}_{\text{3}}{\text{S}}^{\text{-}}$ is less reactive and adds reversibly to the $\text{cyclohex-2-en-1-one}$. The nucleophile adds reversibly to the carbonyl carbon yield the conjugate addition ($\text{1, 4}$ addition) product.

In the first step, ${\text{CH}}_{\text{3}}{\text{S}}^{\text{-}}$ nucleophile from ${\text{CH}}_{\text{3}}\text{SNa}$ add on the $\text{β}$ carbon of the $\text{cyclohex-2-en-1-one}$. This generates an enolate anion.

In the second step, this enolate anion is then protonated by an acid workup.

In the last step, tautomerization takes place and produces a ketone with a conjugate addition product.

Conclusion

Nucleophilic addition of ${\text{CH}}_{\text{3}}{\text{S}}^{\text{-}}$ to the $\text{α,β}$ unsaturated carbonyl produces the major product of the reaction via conjugate addition ($\text{1, 4}$ addition) of the nucleophile.

Interpretation Introduction

(b)

Interpretation:

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

Concept introduction:

The addition reaction mechanism dominates on whether the nucleophile adds to the carbonyl carbon reversibly or irreversibly. Nucleophilic addition is irreversible or reversible depends on charge stability. Nucleophilic addition tends to be irreversible if the negative charge that develops in the adduct is substantially better stabilized than it is in the nucleophile. Nucleophilic addition to a carbonyl carbon tends to be irreversible when it involves a very strong nucleophile like ${\text{R}}^{\text{-}}$ and ${\text{H}}^{\text{-}}$. Otherwise, the nucleophile addition tends to be reversible. In $\text{α,β}$ unsaturated carbonyl undergoes nucleophilic addition, Nucleophile that add reversibly to the carbonyl carbon yields the conjugate addition product as the major product and nucleophile that add irreversibly to the carbonyl carbon yield the direct addition product as the major product.

Answer to Problem 17.24P

The major product and detailed mechanism for the given reaction are:

Explanation of Solution

The given nucleophile ylide is highly reactive and adds irreversibly to the $\text{cyclohex-2-en-1-one}$. The nucleophile adds irreversibly to the carbonyl carbon yield the direct addition ($\text{1, 2}$ addition) product.

In the first step, the given highly reactive ylide attack on the carbonyl carbon of the $\text{cyclohex-2-en-1-one}$ and generates an anion. It is also called betaine formation.

In the second step, the anion coordinates with ${\text{PPh}}_{\text{3}}$ and formed an Oxaphosphetane.

In the last step, Eliminates ${\text{Ph}}_{\text{3}}\text{PO}$ and get direct addition product.

Conclusion

Nucleophilic addition of ylide (Wittig reagent) to the $\text{α,β}$ unsaturated carbonyl produces the major product of the reaction via direct addition ($\text{1, 2}$ addition) of the nucleophile.

Interpretation Introduction

(c)

Interpretation:

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

Concept introduction:

The addition reaction mechanism dominates on whether the nucleophile adds to the carbonyl carbon reversibly or irreversibly. Nucleophilic addition is irreversible or reversible depends on charge stability. Nucleophilic addition tends to be irreversible if the negative charge that develops in the adduct is substantially better stabilized than it is in the nucleophile. Nucleophilic addition to a carbonyl carbon tends to be irreversible when it involves a very strong nucleophile like ${\text{R}}^{\text{-}}$ and ${\text{H}}^{\text{-}}$. Otherwise, the nucleophile addition tends to be reversible. In $\text{α,β}$ unsaturated carbonyl undergoes nucleophilic addition, Nucleophile that add reversibly to the carbonyl carbon yields the conjugate addition product as the major product and nucleophile that add irreversibly to the carbonyl carbon yield the direct addition product as the major product.

Answer to Problem 17.24P

The major product and detailed mechanism for the given reaction are:

Explanation of Solution

The nucleophile ${\text{HCOCH}}_{\text{2}}{}^{\text{-}}$ is less reactive and adds reversibly to the $\text{cyclohex-2-en-1-one}$. The nucleophile adds reversibly to the carbonyl carbon yield the conjugate addition ($\text{1, 4}$ addition) product.

In the first step, ${\text{HCOCH}}_{\text{2}}{}^{\text{-}}$ nucleophile adds on the $\text{β}$ carbon of the $\text{cyclohex-2-en-1-one}$. This generates an enolate anion.

In the second step, this enolate anion is then protonated by an acid workup.

In the last step, tautomerization takes place and produces a ketone with a conjugate addition product.

Conclusion

Nucleophilic addition of ${\text{HCOCH}}_{\text{2}}{}^{\text{-}}$ to the $\text{α,β}$ unsaturated carbonyl produces the major product of the reaction via conjugate addition ($\text{1, 4}$ addition) of nucleophile.

Interpretation Introduction

(d)

Interpretation:

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

Concept introduction:

The addition reaction mechanism dominates on whether the nucleophile adds to the carbonyl carbon reversibly or irreversibly. Nucleophilic addition is irreversible or reversible depends on charge stability. Nucleophilic addition tends to be irreversible if the negative charge that develops in the adduct is substantially better stabilized than it is in the nucleophile. Nucleophilic addition to a carbonyl carbon tends to be irreversible when it involves a very strong nucleophile like ${\text{R}}^{\text{-}}$ and ${\text{H}}^{\text{-}}$. Otherwise, the nucleophile addition tends to be reversible. In $\text{α,β}$ unsaturated carbonyl undergoes nucleophilic addition, Nucleophile that add reversibly to the carbonyl carbon yields the conjugate addition product as the major product and nucleophile that add irreversibly to the carbonyl carbon yield the direct addition product as the major product.

Answer to Problem 17.24P

Explanation of Solution

The given nucleophile ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{}^{\text{-}}$ is highly reactive and adds irreversibly to the $\text{cyclohex-2-en-1-one}$. The nucleophile adds irreversibly to the carbonyl carbon yield the direct addition ($\text{1, 2}$ addition) product

In the first step, ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{}^{\text{-}}$ nucleophile adds on the carbonyl carbon of the $\text{cyclohex-2-en-1-one}$. This generates an anion.

In the second step, this anion is then protonated by acid workup and formed a direct addition product.

Conclusion

Nucleophilic addition of Grignard reagent to the $\text{α,β}$ unsaturated carbonyl produces the major product of the reaction via direct addition ($\text{1, 2}$ addition) of the nucleophile.

Interpretation Introduction

(e)

Interpretation:

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

Concept introduction:

The addition reaction mechanism dominates on whether the nucleophile adds to the carbonyl carbon reversibly or irreversibly. Nucleophilic addition is irreversible or reversible depends on charge stability. Nucleophilic addition tends to be irreversible if the negative charge that develops in the adduct is substantially better stabilized than it is in the nucleophile. Nucleophilic addition to a carbonyl carbon tends to be irreversible when it involves a very strong nucleophile like ${\text{R}}^{\text{-}}$ and ${\text{H}}^{\text{-}}$. Otherwise, the nucleophile addition tends to be reversible. In $\text{α,β}$ unsaturated carbonyl undergoes nucleophilic addition, Nucleophile that add reversibly to the carbonyl carbon yields the conjugate addition product as the major product and nucleophile that add irreversibly to the carbonyl carbon yield the direct addition product as the major product.

Answer to Problem 17.24P

Explanation of Solution

The given nucleophile ${\text{H}}^{\text{-}}$ is highly reactive and adds irreversibly to the $\text{cyclohex-2-en-1-one}$. The nucleophile adds irreversibly to the carbonyl carbon yield the direct addition ($\text{1, 2}$ addition) product

In the first step, ${\text{H}}^{\text{-}}$ nucleophile adds on the carbonyl carbon of the $\text{cyclohex-2-en-1-one}$. This generates an anion.

In the second step, this anion is then protonated by acid workup and formed a direct addition product.

Conclusion

Nucleophilic addition of ${\text{H}}^{\text{-}}$ to the $\text{α,β}$ unsaturated carbonyl produces the major product of the reaction via direct addition ($\text{1, 2}$ addition) of the nucleophile.