Chapter 26, Problem 26.34AP

Interpretation Introduction

(a)

Interpretation:

The reaction between $\text{2-methylpyridine}$ and deuterium oxide is to be completed by giving the major product.

Concept introduction:

Deuterium is an isotope of hydrogen. Deuterium contains one neutron and one proton in its nucleus while hydrogen has only one proton in its nucleus but the number of electrons in hydrogen and deuterium is one.

Isotopic substitution is a reaction in which one isotope is substituted by the other isotope of the same element. Each isotope has its own specific mass which on changing, changes the overall reduced mass of the whole compound.

Answer to Problem 26.34AP

The complete reaction between $\text{2-methylpyridine}$ and deuterium oxide is shown below.

Explanation of Solution

The reaction to be completed is shown below.

Figure 1

When $\text{2-methylpyridine}$ reacts with deuterium oxide in presence of $\text{NaOD}$, the hydrogen atom of methyl group will be abstracted by the base $\text{NaOD}$ and the deuterium will be substituted at its position. The complete reaction is shown below.

Figure 2

Conclusion

The complete reaction between $\text{2-methylpyridine}$ and deuterium oxide is shown in Figure 2.

Interpretation Introduction

(b)

Interpretation:

The reaction between $1H-\text{indole}$ and phenyl lithium is to be completed by giving the major product.

Concept introduction:

Phenyllithium is an organometallic agent which is used to introduce metal into an organic compound during synthesis. It is used to give nucleophilic addition and substitution reactions.

Answer to Problem 26.34AP

The complete reaction between $1H-\text{indole}$ and phenyl lithium is shown below.

Explanation of Solution

The reaction to be completed is shown below.

Figure 3

When indole reacts with phenyllithium, phenyllithium abstracts a proton bonded to nitrogen atom and a lithium salt of indole is formed as a conjugate base. The complete reaction is shown below.

Figure 4

Conclusion

The complete reaction between $1H-\text{indole}$ and phenyl lithium is shown in Figure 4.

Interpretation Introduction

(c)

Interpretation:

The reaction of $\text{1-methylindoline}$ with bromine in dark is to be completed.

Concept introduction:

Electrophilic aromatic substitution reaction involves the substitution of an electrophile on an aromatic ring. The $\text{π-}$ bonds of an aromatic ring makes it electron rich which attracts an electron deficient electrophile towards itself and a substitution reaction takes place.

Answer to Problem 26.34AP

The complete reaction of $\text{1-methylindoline}$ with bromine in dark is shown below.

Explanation of Solution

The reaction to be completed is shown below.

Figure 5

When $\text{1-methylindoline}$ reacts with bromine in dark, bromination occurs on the aromatic ring as in dark, bromination does not occur in aliphatic ring. Therefore, electrophilic aromatic substitution reaction occurs over the aromatic ring on the carbon $\text{-5}$ which is a nucleophilic center. Bromination does not occur at carbon $\text{-3a}$ and carbon $\text{-7}$ due to steric hindrance by hydrogen atom and methyl group respectively.

The complete reaction is shown below.

Figure 6

Conclusion

The complete reaction of $\text{1-methylindoline}$ with bromine in dark is shown in Figure 6.

Interpretation Introduction

(d)

Interpretation:

The reaction of pyrrolizine with hydrogen in presence of platinum and carbon catalyst is to be completed by giving the major product.

Concept introduction:

Catalytic hydrogenation is a reduction process of addition of hydrogen atoms in an alkene or an alkyne by using a metal catalyst. The number of bonds is reduced between carbon atoms.

Answer to Problem 26.34AP

The complete reaction of pyrrolizine with hydrogen in presence of platinum and carbon catalyst is shown below.

Explanation of Solution

The reaction to be completed is shown below.

c

Figure 7

When pyrrolizine reacts with hydrogen in presence of $\text{Pt/C}$, hydrogenation of pyrrolizine takes place. The complete reaction is shown below.

Figure 8

Conclusion

The complete reaction of pyrrolizine with hydrogen in presence of platinum and carbon catalyst is shown in Figure 8.

Interpretation Introduction

(e)

Interpretation:

The reaction of $\text{ethyl}\text{pyridin-2-ylcarbamate}$ with concentrated nitric acid and sulfuric acid is to be completed by giving major product.

Concept introduction:

Nitration is a process in which an aromatic compound is nitrated by electrophilic substitution mechanism in presence of concentrated sulfuric acid and concentrated nitric acid. Electron donating groups substituted on the aromatic ring are those which donate electron to the aromatic ring. Electron donating groups are ortho and para-directing.

Answer to Problem 26.34AP

The complete reaction of $\text{ethyl}\text{pyridin-2-ylcarbamate}$ with concentrated nitric acid and sulfuric acid is shown below.

Explanation of Solution

The reaction to be completed is shown below.

Figure 9

Nitration occurs when $\text{ethyl}\text{pyridin-2-ylcarbamate}$ reacts with concentrated nitric acid and sulfuric acid. The nitro group is substituted at the ortho and para position but the para substituted product is more stable. The complete reaction is shown below.

Figure 10

Conclusion

The complete reaction of $\text{ethyl}\text{pyridin-2-ylcarbamate}$ with concentrated nitric acid and sulfuric acid is shown in Figure 10.

Interpretation Introduction

(f)

Interpretation:

The reaction between $\text{furan-2-yl}\left(\text{thiophen-2-yl}\right)\text{methanone}$ and nitric acid in presence of acetic anhydride is to be completed by giving the major product.

Concept introduction:

Electrophilic aromatic substitution reaction involves the substitution of an electrophile on an aromatic ring. The $\text{π-}$ bonds of an aromatic ring makes it electron rich which attracts an electron deficient electrophile towards itself and a substitution reaction takes place.

Answer to Problem 26.34AP

The complete reaction between $\text{furan-2-yl}\left(\text{thiophen-2-yl}\right)\text{methanone}$ and nitric acid in presence of acetic anhydride is shown below.

Explanation of Solution

The reaction to be completed is shown below.

Figure 11

Electrophilic aromatic substitution reaction will occur in Furan since it is more reactive than thiophene. Therefore, nitration will occur at carbon $\text{-5}$ in Furan. The complete reaction is shown below.

Figure 12

Conclusion

The complete reaction between $\text{furan-2-yl}\left(\text{thiophen-2-yl}\right)\text{methanone}$ and nitric acid in presence of acetic anhydride is shown in Figure 12.

Interpretation Introduction

(g)

Interpretation:

The reaction of $\text{2-methylpyridinium-N-oxide}$ with concentrated ${\text{HNO}}_{\text{3}}$ and concentrated ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ and then with $\text{NaOH}$ is to be completed.

Concept introduction:

Nitration is a process in which an aromatic compound is nitrated by electrophilic substitution mechanism in presence of concentrated sulfuric acid and concentrated nitric acid. Electron donating groups substituted on the aromatic ring are those which donates electron to the aromatic ring. Electron donating groups are ortho and para-directing.

Answer to Problem 26.34AP

The complete reaction of $\text{2-methylpyridineoxide}$ with concentrated ${\text{HNO}}_{\text{3}}$ and concentrated ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ and then with $\text{NaOH}$ is shown below.

Explanation of Solution

The reaction to be completed is shown below.

Figure 13

The pyridine ring activates towards electrophilic aromatic substitution due to the presence of pyridinium $\text{-N-oxide}$. The nitration occurs at the carbon $\text{-4}$ as it is more stable than ortho position. The complete reaction is shown below.

Figure 14

Conclusion

The complete reaction of $\text{2-methylpyridineoxide}$ with concentrated ${\text{HNO}}_{\text{3}}$ and concentrated ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ and then with $\text{NaOH}$ is shown in Figure 14.

Interpretation Introduction

(h)

Interpretation:

The reaction of $\text{1-}\left(\text{pyridin-3-yl}\right)\text{ethanone}$ with hydrazine is to be completed by giving the major product.

Concept introduction:

Wolff Kishner reduction is a reaction in which aldehydes and ketones are converted into alkanes on reaction with hydrazine, $\text{KOH}$, and on heating. Carbonyl compound is condensed on heating with hydrazine to form hydrazone. The base, $\text{KOH}$ reduces the carbon into alkane and oxidizes the hydrazine to nitrogen gas.

Answer to Problem 26.34AP

The complete reaction of $\text{1-}\left(\text{pyridin-3-yl}\right)\text{ethanone}$ with hydrazine is shown below.

Explanation of Solution

The reaction to be completed is shown below.

Figure 15

The Wolff-Kishner reduction takes place when $\text{1-}\left(\text{pyridin-3-yl}\right)\text{ethanone}$ reacts with hydrazine in presence of a base to form a hydrazone. The complete reaction is shown below.

Figure 16

Conclusion

The complete reaction of $\text{1-}\left(\text{pyridin-3-yl}\right)\text{ethanone}$ with hydrazine is shown in Figure 16.