Chapter 12.11, Problem 27P

(a)

Interpretation Introduction

Interpretation: The major product of the given reaction has to be found.

Concept Introduction:

Major product in the reaction of $\alpha ,\beta -$ unsaturated carbonyl compounds with weak bases:

$\text{α,β-}$ Unsaturated carbonyl compounds on reaction with weak bases gives conjugate addition products as the major products as shown in the following general scheme:

General scheme:

  

It can be observed that the conjugate addition product has been formed by the addition of basic anion to the beta-carbon atom and that of hydrogen atom to the alpha-carbon carbon atom.

The examples for the weak bases are:

$\begin{array}{l}•\text{HBr}\\ •{\text{CH}}_{\text{3}}\text{SH}\\ •{\text{CH}}_{\text{3}}\text{OH}\\ •{\text{NH}}_3\end{array}$

(b)

Interpretation Introduction

Interpretation: The major product of the given reaction has to be found.

Concept Introduction:

Major product in the reaction of $\alpha ,\beta -$ unsaturated carbonyl compounds with weak bases:

$\text{α,β-}$ Unsaturated carbonyl compounds on reaction with weak bases gives conjugate addition products as the major products as shown in the following general scheme:

General scheme:

It can be observed that the conjugate addition product has been formed by the addition of basic anion to the beta-carbon atom and that of hydrogen atom to the alpha-carbon carbon atom.

The examples for the weak bases are:

$\begin{array}{l}•\text{HBr}\\ •{\text{CH}}_{\text{3}}\text{SH}\\ •{\text{CH}}_{\text{3}}\text{OH}\\ •{\text{NH}}_3\end{array}$

(c)

Interpretation Introduction

Interpretation: The major product of the given reaction has to be found.

Concept Introduction:

Major product in the reaction of $\alpha ,\beta -$ unsaturated carbonyl compounds with weak bases:

$\text{α,β-}$ Unsaturated carbonyl compounds on reaction with weak bases gives conjugate addition products as the major products as shown in the following general scheme:

General scheme:

It can be observed that the conjugate addition product has been formed by the addition of basic anion to the beta-carbon atom and that of hydrogen atom to the alpha-carbon carbon atom.

The examples for the weak bases are:

$\begin{array}{l}•\text{HBr}\\ •{\text{CH}}_{\text{3}}\text{SH}\\ •{\text{CH}}_{\text{3}}\text{OH}\\ •{\text{NH}}_3\end{array}$

Major product in the reaction of $\alpha ,\beta -$ unsaturated carbonyl compounds with strong bases:

$\text{α,β-}$ Unsaturated carbonyl compounds on reaction with strong bases gives direct addition products as the major products as shown in the following general scheme:

General scheme:

It can be observed that the direct addition product has been formed from the direct reaction of the strong base with the carbonyl functional group of the $\text{α,β-}$ unsaturated carbonyl compounds.

The examples for the strong bases are:

$\begin{array}{l}•{}^{-}{\text{CH}}_3{\text{Mg}}^{2+}{\text{Br}}^{-}\Rightarrow \text{Gignard}\text{reagent}\\ •{\text{NaBH}}_4\Rightarrow {\text{H}}^{\text{-}}\text{hydride}\text{donor}\end{array}$

(d)

Interpretation Introduction

Interpretation: The major product of the given reaction has to be found.

Concept Introduction:

Major product in the reaction of $\alpha ,\beta -$ unsaturated carbonyl compounds with weak bases:

$\text{α,β-}$ Unsaturated carbonyl compounds on reaction with weak bases gives conjugate addition products as the major products as shown in the following general scheme:

General scheme:

It can be observed that the conjugate addition product has been formed by the addition of basic anion to the beta-carbon atom and that of hydrogen atom to the alpha-carbon carbon atom.

The examples for the weak bases are:

$\begin{array}{l}•\text{HBr}\\ •{\text{CH}}_{\text{3}}\text{SH}\\ •{\text{CH}}_{\text{3}}\text{OH}\\ •{\text{NH}}_3\end{array}$

Major product in the reaction of $\alpha ,\beta -$ unsaturated carbonyl compounds with strong bases:

$\text{α,β-}$ Unsaturated carbonyl compounds on reaction with strong bases gives direct addition products as the major products as shown in the following general scheme:

General scheme:

It can be observed that the direct addition product has been formed from the direct reaction of the strong base with the carbonyl functional group of the $\text{α,β-}$ unsaturated carbonyl compounds.

The examples for the strong bases are:

$\begin{array}{l}•{}^{-}{\text{CH}}_3{\text{Mg}}^{2+}{\text{Br}}^{-}\Rightarrow \text{Gignard}\text{reagent}\\ •{\text{NaBH}}_4\Rightarrow {\text{H}}^{\text{-}}\text{hydride}\text{donor}\end{array}$