Chapter 19, Problem 19.64AP

Interpretation Introduction

(a)

Interpretation:

The curved arrow mechanism for the given reaction is to be stated.

Concept introduction:

The curved-arrow notation is used to show the transfer of electrons from one atom to another. The curved arrow has two barbs (head and tail) which represent the direction of electron flow.

Answer to Problem 19.64AP

The curved arrow mechanism for the given reaction is shown below.

Explanation of Solution

The given reaction is shown below.

Figure 1

In the above reaction, diphenylmethanethione undergoes hydrolysis to yield benzophenone.

The curved arrow mechanism for the reaction is shown below.

Figure 2

In the above mechanism, lone pairs of water attacks the $\text{π}$ bonded electrons of carbon and sulphur of diphenylmethanethione to yield a thiol. The thiol generated abstracts the proton from hydronium ion to give protonated thiol group. Now this protonated thiol group acts as a leaving group and gets eliminated from the molecule to yield benzophenone.

Conclusion

The curved arrow mechanism for the reaction is shown in Figure 2.

Interpretation Introduction

(b)

Interpretation:

The curved arrow mechanism for the given reaction is to be stated.

Concept introduction:

The curved-arrow notation is used to show the transfer of electrons from one atom to another. The curved arrow has two barbs (head and tail) which represent the direction of electron flow.

Answer to Problem 19.64AP

The curved arrow mechanism for the given reaction is shown below.

Explanation of Solution

The given reaction is shown below.

Figure 3

In the above reaction, trimethylphosphite reacts with $2-\text{methyloxirane}$ to form propene.

The curved arrow mechanism for the given reaction is shown below.

Figure 4

In the above mechanism, the trimethylphosphite reacts the least hindered site of the epoxide ring. This attacks leads to the formation of an intermediate betaine. The betaine molecule undergoes rearrangement to yield a cyclic compound oxaphosphetane. In the next step the ring opening of oxaphosphetane takes place to yield propene.

Conclusion

The curved arrow mechanism for the given reaction is shown in Figure 4.

Interpretation Introduction

(c)

Interpretation:

The curved arrow mechanism for the given reaction is to be stated.

Concept introduction:

The curved-arrow notation is used to show the transfer of electrons from one atom to another. The curved arrow has two barbs (head and tail) which represent the direction of electron flow.

Answer to Problem 19.64AP

The curved arrow mechanism for the given reaction is shown below.

Explanation of Solution

The given reaction is shown below.

Figure 5

In the above reaction, ethylamine reacts with $3,3-\text{dimethylpentanedial}$ to yield $1-\text{ethyl}-4,4-\text{dimethyl}-1,4-\text{dihydropyridine}$.

The curved arrow mechanism for the given reaction is shown below.

Figure 6

In the above mechanism, the carbonyl carbon of $3,3-\text{dimethylpentanedial}$ attacks the proton of acid catalyst to gives the protonated aldehye. The lone pairs of ethylamine then attacks the electrophilic carbon. This attacks leads to the attachment of the amine group to the carbonyl carbon. The rearrangement takes place and there is removal of water. After the removal of water cyclisation takes place which leads to the formation of the $1-\text{ethyl}-4,4-\text{dimethyl}-1,4-\text{dihydropyridine}$.

Conclusion

The curved arrow mechanism for the given reaction is shown in Figure 6.

Interpretation Introduction

(d)

Interpretation:

The curved arrow mechanism for the given reaction is to be stated.

Concept introduction:

The curved-arrow notation is used to show the transfer of electrons from one atom to another. The curved arrow has two barbs (head and tail) which represent the direction of electron flow.

Answer to Problem 19.64AP

The curved arrow mechanism for the given reaction is shown below.

Explanation of Solution

The given reaction is shown below.

Figure 7

In the above reaction, $\left(R\right)-3,7-\text{dimethyloct}-6-\text{enal}$ reacts in the presence of acid catalyst to yield $\left(5R\right)-5-\text{methyl}-2-\left(\text{prop}-1-\text{en}-2-\text{yl}\right)\text{cyclohexanol}$.

The curved arrow mechanim for the given reaction is shown below.

Figure 8

In the above mechanism, the carbonyl carbon of the compound $\left(R\right)-3,7-\text{dimethyloct}-6-\text{enal}$ attacks the proton from the acid catalyst to give a protonated aldehyde. This protonated aldehyde undergoes rearrangement to yield a cyclic structure which on deprotonation yields the required compound $\left(5R\right)-5-\text{methyl}-2-\left(\text{prop}-1-\text{en}-2-\text{yl}\right)\text{cyclohexanol}$.

Conclusion

The curved arrow mechanism of the giveh reaction is shown in Figure 8.

Interpretation Introduction

(d)

Interpretation:

The curved arrow mechanism for the given reaction is to be stated.

Concept introduction:

The curved-arrow notation is used to show the transfer of electrons from one atom to another. The curved arrow has two barbs (head and tail) which represent the direction of electron flow.

Answer to Problem 19.64AP

The curved arrow mechanism for the given reaction is shown below.

Explanation of Solution

The given reaction is shown below.

Figure 9

In the above reaction, acetaldehyde in the presence of acid catalyst yields a compound paraldehyde.

The curved arrow mechanism for the given reaction is shown below.

Figure 10

In the above mechanism, the acetaldehyde attacks the proton of acid catalyst to yield protonated acetaldehyde. The three moles of protonated acetaldehyde combines with each other to gives a cyclic structure. This cyclic structure on rearrangement gives the required product paraldehyde.

Conclusion

The curved arrow mechanism of the given reaction is shown in Figure 10.