Chapter 17, Problem 17.60P

Interpretation Introduction

(a)

Interpretation:

For the given reaction, the major product and reaction mechanism is to be drawn.

Concept introduction:

The weak resonance contributor with separated charges generates a small partial positive charge on the beta carbon in the resonance hybrid. Thus, a nucleophile can attack at either the carbonyl carbon or the beta carbon. A polar $\text{π}$ bond that is alpha, beta-unsaturated is susceptible to a nucleophilic attack at both the electron-poor atom of the polar $\text{π}$ bond and the beta carbon. Attack at the carbonyl carbon yields the direct addition (or 1, 2—addition) product whereas attack at the beta carbon yields the conjugate addition (or 1, 4-addition). Direct addition to an alpha, beta-unsaturated polar $\text{π}$ bond dominates if the nucleophile adds irreversibly to the polar $\text{π}$ bond. Otherwise, conjugate addition is favored.

Answer to Problem 17.60P

The nucleophile adds reversibly and undergoes a 1, 4-addition reaction.

Explanation of Solution

The weak resonance contributor with separated charges generates a small partial positive charge on the beta carbon in the resonance hybrid. Thus, a nucleophile can attack at either the carbonyl carbon or the beta carbon. A polar $\text{π}$ bond that is alpha, beta-unsaturated is susceptible to a nucleophilic attack at both the electron-poor atom of the polar $\text{π}$ bond and the beta carbon.

In this reaction, both carbonyl carbon as well as beta carbon are electrophilic. Here the nucleophile adds reversibly; therefore, this reaction undergoes 1, 4-addition. In this reaction, ${\text{O}}^{-}$ atom forms in the nucleophilic addition step. It is then protonated in a subsequent proton transfer reaction to form uncharged alcohol. The reaction mechanism is shown below:

Here the enol tautomerizes back to the ketone via back to back proton transfer steps. It is represented as below:

Conclusion

From the location of the electrophilic carbon, the major product for the given reaction is predicted, and the reaction mechanism is drawn.

Interpretation Introduction

(b)

Interpretation:

For the given reaction, the major product and the reaction mechanism is to be drawn.

Concept introduction:

The weak resonance contributor with separated charges generates a small partial positive charge on the beta carbon in the resonance hybrid. Thus, a nucleophile can attack at either the carbonyl carbon or the beta carbon. A polar $\text{π}$ bond that is alpha, beta-unsaturated is susceptible to a nucleophilic attack at both the electron-poor atom of the polar $\text{π}$ bond and the beta carbon. Attack at the carbonyl carbon yields the direct addition (or 1, 2—addition) product whereas attack at the beta carbon yields the conjugate addition (or 1, 4-addition). Direct addition to an alpha, beta-unsaturated polar $\text{π}$ bond dominates if the nucleophile adds irreversibly to the polar $\text{π}$ bond. Otherwise, conjugate addition is favored.

Answer to Problem 17.60P

The nucleophile adds irreversibly and undergoes a 1, 2-addition reaction.

Explanation of Solution

A polar $\text{π}$ bond that is alpha, beta-unsaturated is susceptible to a nucleophilic attack at both the electron-poor atom of the polar $\text{π}$ bond and the beta carbon. Attack at the carbonyl carbon yields the direct addition (or 1, 2—addition) product whereas attack at the beta carbon yields the conjugate addition (or 1, 4-addition). Direct addition to an alpha, beta-unsaturated polar $\text{π}$ bond dominates if the nucleophile adds irreversibly to the polar $\text{π}$ bond. Otherwise, conjugate addition is favored.

In this reaction, the nucleophile adds irreversibly; hence this reaction undergoes direction addition (1, 2-addition). In this reaction, ${\text{O}}^{-}$ atom forms in the nucleophilic addition step. It is then protonated in a subsequent proton transfer reaction to form uncharged alcohol. The reaction mechanism is shown below:

Conclusion

From the location of the electrophilic carbon, the major product for the given reaction is predicted, and the reaction mechanism is drawn.

Interpretation Introduction

(c)

Interpretation:

For the given reaction, the major product and the reaction mechanism is to be drawn.

Concept introduction:

The weak resonance contributor with separated charges generates a small partial positive charge on the beta carbon in the resonance hybrid. Thus, a nucleophile can attack at either the carbonyl carbon or the beta carbon. A polar $\text{π}$ bond that is alpha, beta-unsaturated is susceptible to a nucleophilic attack at both the electron-poor atom of the polar $\text{π}$ bond and the beta carbon. Attack at the carbonyl carbon yields the direct addition (or 1, 2—addition) product whereas attack at the beta carbon yields the conjugate addition (or 1, 4-addition). Direct addition to an alpha, beta-unsaturated polar $\text{π}$ bond dominates if the nucleophile adds irreversibly to the polar $\text{π}$ bond. Otherwise, conjugate addition is favored.

Answer to Problem 17.60P

The nucleophile adds irreversibly and undergoes a 1, 2-addition reaction.

Explanation of Solution

A polar $\text{π}$ bond that is alpha, beta-unsaturated is susceptible to a nucleophilic attack at both the electron-poor atom of the polar $\text{π}$ bond and the beta carbon. Attack at the carbonyl carbon yields the direct addition (or 1, 2—addition) product whereas attack at the beta carbon yields the conjugate addition (or 1, 4-addition). Direct addition to an alpha, beta-unsaturated polar $\text{π}$ bond dominates if the nucleophile adds irreversibly to the polar $\text{π}$ bond. Otherwise, conjugate addition is favored.

In this reaction, the nucleophile adds irreversibly; hence this reaction undergoes direct addition (1, 2-addition). Here ${\text{O}}^{-}$ atom forms in the nucleophilic addition step. The O^- is then protonated in a subsequent proton transfer reaction to form uncharged alcohol. The reaction mechanism is shown below:

Conclusion

From the location of the electrophilic carbon, the major product for the given reaction is predicted, and the reaction mechanism is drawn.

Interpretation Introduction

(d)

Interpretation:

For the given reaction, the major product and the reaction mechanism is to be drawn.

Concept introduction:

The weak resonance contributor with separated charges generates a small partial positive charge on the beta carbon in the resonance hybrid. Thus, a nucleophile can attack at either the carbonyl carbon or the beta carbon. A polar $\text{π}$ bond that is alpha, beta-unsaturated is susceptible to a nucleophilic attack at both the electron-poor atom of the polar $\text{π}$ bond and the beta carbon. Attack at the carbonyl carbon yields the direct addition (or 1, 2—addition) product whereas attack at the beta carbon yields the conjugate addition (or 1, 4-addition). Direct addition to an alpha, beta-unsaturated polar $\text{π}$ bond dominates if the nucleophile adds irreversibly to the polar $\text{π}$ bond. Otherwise, conjugate addition is favored.

Answer to Problem 17.60P

The nucleophile adds irreversibly and undergoes a 1, 4-addition reaction.

Explanation of Solution

The weak resonance contributor with separated charges generates a small partial positive charge on the beta carbon in the resonance hybrid. Thus, a nucleophile can attack at either the carbonyl carbon or the beta carbon. A polar $\text{π}$ bond that is alpha, beta-unsaturated is susceptible to a nucleophilic attack at both the electron-poor atom of the polar $\text{π}$ bond and the beta carbon.

In this reaction, both carbonyl carbon as well as beta carbon are electrophilic. In this reaction, the nucleophile adds reversibly; therefore this reaction undergoes 1, 4-addition. In this reaction, ${\text{O}}^{-}$ atom forms in the nucleophilic addition step. It is then protonated in a subsequent proton transfer reaction to form uncharged alcohol. The reaction mechanism is shown below:

Here the enol tautomerizes back to the ketone via back to back proton transfer steps. It is shown below:

Conclusion

From the location of the electrophilic carbon, the major product for the given reaction is predicted, and the reaction mechanism is drawn.

Interpretation Introduction

(e)

Interpretation:

For the given reaction, the major product and the reaction mechanism is to be drawn.

Concept introduction:

The weak resonance contributor with separated charges generates a small partial positive charge on the beta carbon in the resonance hybrid. Thus, a nucleophile can attack at either the carbonyl carbon or the beta carbon. A polar $\text{π}$ bond that is alpha, beta-unsaturated is susceptible to a nucleophilic attack at both the electron-poor atom of the polar $\text{π}$ bond and the beta carbon. Attack at the carbonyl carbon yields the direct addition (or 1, 2—addition) product whereas attack at the beta carbon yields the conjugate addition (or 1, 4-addition). Direct addition to an alpha, beta-unsaturated polar $\text{π}$ bond dominates if the nucleophile adds irreversibly to the polar $\text{π}$ bond. Otherwise, conjugate addition is favored.

Answer to Problem 17.60P

The nucleophile adds irreversibly and undergoes a 1, 4-addition reaction.

Explanation of Solution

The weak resonance contributor with separated charges generates a small partial positive charge on the beta carbon in the resonance hybrid. Thus, a nucleophile can attack at either the carbonyl carbon or the beta carbon. A polar $\text{π}$ bond that is alpha, beta-unsaturated is susceptible to a nucleophilic attack at both the electron-poor atom of the polar $\text{π}$ bond and the beta carbon.

In this reaction, both carbonyl carbon as well as beta carbon are electrophilic. In this reaction, the nucleophile adds reversibly; therefore this reaction undergoes 1, 4-addition. In this reaction, ${\text{O}}^{-}$ atom forms in the nucleophilic addition step. It is then protonated in a subsequent proton transfer reaction to form uncharged alcohol. The reaction mechanism is shown below:

Here the enol tautomerizes back to the ketone via back to back proton transfer steps. It is shown below:

Conclusion

From the location of the electrophilic carbon, the major product for the given reaction is predicted, and the reaction mechanism is drawn.