Chapter 17, Problem 17.43P

Interpretation Introduction

(a)

Interpretation:

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

Concept introduction:

Lithium aluminium hydride (LAH) or ${\text{LiAlH}}_{\text{4}}$ and sodium borohydride (${\text{NaBH}}_{\text{4}}$) are common sources of the nucleophilic hydride ion (${\text{H}}^{\text{-}}$). They are commonly used to reduce carbonyl compounds into the corresponding alcohols. An aldehyde is reduced to a primary alcohol, and a ketone is reduced to a secondary alcohol in the presence of a protic solvent like water (${\text{H}}_{\text{2}}\text{O}$).

The chemical behaviour of deuterium (${\text{D or }}^2\text{H}$) is basically identical to that of hydrogen. Therefore, ${\text{D}}_{\text{2}}\text{O}$ behaves the same as ${\text{H}}_{\text{2}}\text{O}$, and ${\text{LiAlD}}_{\text{4}}$ behaves the same as ${\text{LiAlH}}_{\text{4}}$.

Answer to Problem 17.43P

The detailed mechanism for the given reaction is

The major product of the given reaction:

Explanation of Solution

The given reaction is

${\text{LiAlH}}_{\text{4}}$ is the source of ${\text{H}}^{\text{-}}$ ion; this reagent is used to reduce a ketone to a secondary alcohol. The first step of the mechanism involves the addition of the nucleophile, hydride ion, to the electrophilic carbonyl carbon from ketone. An alkoxide ion is created in this step.

This alkoxide ion then attacks the deuterium (${\text{D}}^{\text{+}}$) of the deuterated, water which is the solvent used.

Thus, the final product of the given reaction is the secondary alcohol shown below:

Conclusion

A ketone, when treated with a reducing agent such as Lithium aluminium hydride (LAH) or ${\text{LiAlH}}_{\text{4}}$ and sodium borohydride (${\text{NaBH}}_{\text{4}}$), reduces to form a secondary alcohol.

Interpretation Introduction

(b)

Interpretation:

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

Concept introduction:

Lithium aluminium hydride (LAH) or ${\text{LiAlH}}_{\text{4}}$ and sodium borohydride (${\text{NaBH}}_{\text{4}}$) are common sources of the nucleophilic hydride ion (${\text{H}}^{\text{-}}$). They are commonly used to reduce carbonyl compounds into the corresponding alcohols. An aldehyde is reduced to a primary alcohol, and a ketone is reduced to a secondary alcohol in the presence of a protic solvent like water (${\text{H}}_{\text{2}}\text{O}$).

The chemical behaviour of deuterium (${\text{D or }}^2\text{H}$) is really identical to that of hydrogen. Therefore, ${\text{D}}_{\text{2}}\text{O}$ behaves the same as ${\text{H}}_{\text{2}}\text{O}$, and ${\text{LiAlD}}_{\text{4}}$ behaves the same as ${\text{LiAlH}}_{\text{4}}$.

Answer to Problem 17.43P

The detailed mechanism for the given reaction is

The major product of the given reaction:

Explanation of Solution

The given reaction is

${\text{LiAlD}}_{\text{4}}$ behaves the same as the ${\text{LiAlH}}_{\text{4}}$ and is the source of ${\text{D}}^{\text{-}}$ ion. This reagent is used to reduce a ketone to a secondary alcohol. The first step of the mechanism involves the addition of the nucleophile, hydride ion, to the electrophilic carbonyl carbon from ketone. An alkoxide ion is formed in this step.

This alkoxide ion then attacks the proton (H) of water, which is the solvent used in the next step.

Thus, the final product of the given reaction is the secondary alcohol shown below:

Conclusion

A ketone, when treated with a reducing agent such as Lithium aluminium hydride (LAH) or ${\text{LiAlH}}_{\text{4}}$ and sodium borohydride (${\text{NaBH}}_{\text{4}}$), reduces to form a secondary alcohol.

Interpretation Introduction

(c)

Interpretation:

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

Concept introduction:

Lithium aluminium hydride (LAH) or ${\text{LiAlH}}_{\text{4}}$ and sodium borohydride (${\text{NaBH}}_{\text{4}}$) are common sources of the nucleophilic hydride ion (${\text{H}}^{\text{-}}$). They are commonly used to reduce carbonyl compounds into the corresponding alcohols. An aldehyde is reduced to a primary alcohol, and a ketone is reduced to a secondary alcohol in the presence of a protic solvent like water (${\text{H}}_{\text{2}}\text{O}$).

The chemical behaviour of deuterium (${\text{D or }}^2\text{H}$) is basically identical to that of hydrogen. Therefore, ${\text{D}}_{\text{2}}\text{O}$ behaves the same as ${\text{H}}_{\text{2}}\text{O}$, and ${\text{LiAlD}}_{\text{4}}$ behaves the same as ${\text{LiAlH}}_{\text{4}}$.

Answer to Problem 17.43P

The detailed mechanism for the given reaction is

The major product of the given reaction:

Explanation of Solution

The given reaction is

${\text{LiAlD}}_{\text{4}}$ behaves the same as the ${\text{LiAlH}}_{\text{4}}$ and is the source of ${\text{D}}^{\text{-}}$ ion. This reagent is used to reduce a ketone to a secondary alcohol. The first step of the mechanism involves the addition of the nucleophile, hydride ion, to the electrophilic carbonyl carbon from ketone. An alkoxide ion is made in this step.

This alkoxide ion then attacks the deuterium (${\text{D}}^{\text{+}}$) of the deuterated water, which is the solvent used.

Thus, the final product of the given reaction is the secondary alcohol shown below:

Conclusion

A ketone, when treated with a reducing agent such as Lithium aluminium hydride (LAH) or ${\text{LiAlH}}_{\text{4}}$ and sodium borohydride (${\text{NaBH}}_{\text{4}}$), reduces to form a secondary alcohol.