Chapter 18, Problem 18.58P

Interpretation Introduction

(a)

Interpretation:

The complete, detailed mechanism of a given reaction under strongly acidic condition is to be drawn and major organic product is to be predicted.

Concept introduction:

When an aldehyde or ketone is treated with an alcohol under acidic conditions, the hemiacetal product is formed. By using an excess amount of alcohol under acidic conditions, nucleophilic addition produces hemiacetal, which further forms an acetal. The acetal has two alkoxy groups bonded to the same carbon. The formation of the acetal product is favored by using excess alcohol. In the hydrolysis of acetal reaction, addition of water results in the breaking of $\text{C-OR}$ bonds. The hydrolysis reaction of acetal produces ketone as a major product.

Answer to Problem 18.58P

The complete, detailed mechanism of a given reaction in the acidic medium is shown below and ketone is a major product.

Explanation of Solution

The given reaction is

This is an acetal hydrolysis reaction under strongly acidic conditions to produce ketone as a major product. The leaving group is an uncharged alcohol and water acts as the nucleophile.

In the first step, the lone pairs on the O atom abstract the proton from water, which makes positively charged O ion.

In the next step, the bond between positively charged O and C breaks and forms a new double bond in another $\text{C-O}$ bond.

Next, nucleophile water attacks on the electropositive carbon atom in the nucleophilic addition reaction.

In the deprotonation step, water abstracts the H atom and produces a hemiacetal group.

The lone pairs on $\text{O}$ atom accept the proton in the protonation step by generating a diol as a good leaving group.

The diol leaving group departs and forms resonance stabilized carbocation.

Water nucleophile abstracts the proton from the $\text{OH}$ and forms ketone as a product.

The complete, detailed mechanism of a given reaction in the acidic medium is shown below and ketone is a major product.

Conclusion

The complete, detailed mechanism of the given reaction under acidic medium and excess water is drawn.

Interpretation Introduction

(b)

Interpretation:

The complete, detailed mechanism of a given reaction under stongly acidic condition is to be drawn and major organic product is to be predicted.

Concept introduction:

When an aldehyde or ketone is treated with an alcohol under acidic conditions, the hemiacetal product is formed. By using an excess amount of alcohol under acidic conditions, after that nucleophilic addition produces hemiacetal, which further forms an acetal. The acetal has two alkoxy groups are bonded to the same carbon. The formation of the acetal product is favored by using excess alcohol. In the hydrolysis of acetal reaction, because of the addition of water results in the breaking of $\text{C-OR}$ bonds.

The hydrolysis reaction of acetal produces ketone as a major product.

Answer to Problem 18.58P

The complete, detailed mechanism of a given reaction in the acidic medium is shown below and ketone is a major product.

Explanation of Solution

The given reaction is

This is an acetal hydrolysis reaction under strongly acidic condition, not strong bases should appear to produce ketone as a major product. The leaving group is an uncharged alcohol, and water acts as the nucleophile.

In the first step, the lone pairs on the O atom abstract the proton from water, which makes positively charged O ion.

In the next step, the bond between positively charged O and C breaks and forms a new double bond in another $\text{C-OR}$ bond.

Next, nucleophile water attacks the electropositive carbon atom in the nucleophilic addition reaction.

In the deprotonation step, water abstracts the H atom and produces a hemiacetal group.

The lone pairs on $\text{O}$ atom accept the proton in the protonation step by generating methanol as a good leaving group.

The methanol leaving group departs and form resonance stabilized carbocation.

water nucleophile abstracts the proton from the amino group and makes ketone as a product.

The complete, detailed mechanism of a given reaction under acidic medium is shown below and a ketone is a major product.

Conclusion

The complete, detailed mechanism of given reaction under acidic medium and excess water is drawn.

Interpretation Introduction

(c)

Interpretation:

The complete, detailed mechanism of a given reaction under strongly acidic condition is to be drawn and major organic product is to be predicted.

Concept introduction:

In the hydrolysis of nitriles reaction, addition of water results in the breaking of $\text{R-C}\equiv \text{N}$ bonds under strongly acidic condition. The treatment of nitriles with water under the basic or acidic conditions results in a primary amide. Under acidic conditions mechanism consist of five elementary steps, the only step is not a proton transfer is the nucleophilic addition steps on the electropositive carbon.

Answer to Problem 18.58P

The complete, detailed mechanism of a given reaction in the acidic medium is shown below and amide is a major product.

Explanation of Solution

The given reaction is

This is a nitrile hydrolysis reaction under the strongly acidic condition to produce an amide as a major product. The nitrile group is protonated first and water act as the nucleophile.

In the first step, the lone pairs on the N atom abstract the proton from water, which makes positively charged N ion.

Next, nucleophile water attacks on the electropositive carbon atom in the nucleophilic addition reaction.

In the deprotonation step, water abstracts the H atom in the protonation step.

The lone pairs on N atom accept the proton in the protonation step by generating an amino group.

The nucleophile water abstracts the proton in the resonance stabilized carbocation and produces amide as a major product.

The complete, detailed mechanism of a given reaction under the strongly acidic medium is shown below and an amide is a major product.

Conclusion

The complete, detailed mechanism of given reaction under acidic medium and excess water is drawn.

Interpretation Introduction

(d)

Interpretation:

The complete, detailed mechanism of a given reaction under stongly acidic condition is to be drawn and major organic product is to be predicted.

Concept introduction:

When an aldehyde or ketone is treated with an alcohol under acidic conditions, the hemiacetal product is formed. By using an excess amount of alcohol under acidic conditions the hemiacetals, nucleophilic addition produces hemiacetal, which further form an acetal. The acetal has two alkoxy groups are bonded to the same carbon. The formation of the acetal product is favored by using excess alcohol. In the hydrolysis of acetal reaction, addition of water results in the breaking of $\text{C-OR}$ bonds. The hydrolysis reaction of acetal produces ketone as a major product.

Answer to Problem 18.58P

The complete, detailed mechanism of a given reaction in the acidic medium is shown below and ketone is a major product.

Explanation of Solution

The given reaction is

This is an acetal hydrolysis reaction under strongly acidic condition, not strong bases should appear to produce ketone as a major product. The leaving group is an uncharged alcohol and water acts as the nucleophile.

In the first step, the lone pairs on the O atom abstract the proton from water, which makes positively charged O ion as a good leaving group.

In the next step, the ethanol good leaving group departs and forms a new double bond in another $\text{C-O}$ bond.

Next, nucleophile water attacks on the electropositive carbon atom in the nucleophilic addition reaction.

In the deprotonation step, water abstracts the H atom and produces a hemiacetal group.

The lone pairs on $\text{O}$ atom accept the proton in the protonation step by generating ethanol as a good leaving group.

In the next step, the ethanol good leaving group departs and forms resonance stabilized carbocation.

Water nucleophile abstracts the proton from the carbon ring and forms ketone as a product.

The complete, detailed mechanism of a given reaction in the acidic medium is shown below and ketone is a major product.

Conclusion

The complete, detailed mechanism of given reaction under acidic medium and excess water is drawn.