Chapter 17, Problem 17.28AP

Interpretation Introduction

(a)

Interpretation:

The preparation method of benzyl methyl ether from toluene is to be stated.

Concept introduction:

Cyclic alkenes on reaction with N-Bromosuccinimide (NBS) forms allyl or benzyl bromide, that is, bromine is substituted at the allylic or benzylic position. NBS is a rich source of free radical of $\text{Br}$. The mechanism followed by NBS is a radical substitution reaction.

Answer to Problem 17.28AP

The preparation method of benzyl methyl ether from toluene is shown below.

Explanation of Solution

For preparing benzyl methyl ether from toluene, toluene is first brominated.

For bromination of toluene, $N-$ bromosuccinamide (NBS) is used in ${\text{CCl}}_4$. Benzyl bromide on reaction with strong base gives the substituted ether.

The corresponding reaction sequences are shown below.

Figure 1

Conclusion

The preparation method of benzyl methyl ether from toluene is shown in Figure 1.

Interpretation Introduction

(b)

Interpretation:

The preparation method of $3-\text{phenyl}-1-\text{propanol}$ from toluene is to be stated.

Concept introduction:

Cyclic alkenes on reaction with N-Bromosuccinimide (NBS) forms allyl or benzyl bromide, that is, bromine is substituted at the allylic or benzylic position. NBS is a rich source of free radical of $\text{Br}$. The mechanism followed by NBS is a radical substitution reaction.

Answer to Problem 17.28AP

The preparation method of $3-\text{phenyl}-1-\text{propanol}$ from toluene is shown below.

Explanation of Solution

In given reaction, toluene is first brominated with NBS (N-bromosuccinamide). Brominated benzyl reacts with Grignard reagent and epoxide to produce the required alcohol. This is a ring opening reaction.

The corresponding reaction sequences to obtain the desired product are shown below.

Figure 2

Conclusion

The preparation method of $3-\text{phenyl}-1-\text{propanol}$ from toluene is shown in Figure 2.

Interpretation Introduction

(c)

Interpretation:

The preparation method of $\left(Z\right)-1,4-\text{nanodiene}$ from $1-\text{hexyne}$ is to be stated.

Concept introduction:

The Lindlar’s catalyst is composed of ${\text{H}}_{\text{2}}$ over platinum, traces of lead and quinoline. Lead and quinoline poisons the activity of this catalyst, so, that it reduces an alkyne into an alkene. The Lindlar’s catalyst is used to reduce the alkynes to form the cis-alkenes.

Answer to Problem 17.28AP

The preparation method of $\left(Z\right)-1,4-\text{nanodiene}$ from $1-\text{hexyne}$ is shown below.

Explanation of Solution

The addition of $3-\text{bromoprop}-1-\text{ene}$ gives addition reaction with $1-\text{hexyne}$. This product is further reduced to $\left(Z\right)-1,4-\text{nanodiene}$ with the help of Lindlar catalyst.

The corresponding reaction sequences to obtain the desired product are shown below.

Figure 3

Conclusion

The preparation method of $\left(Z\right)-1,4-\text{nanodiene}$ from $1-\text{hexyne}$ is shown in Figure 3.

Interpretation Introduction

(d)

Interpretation:

The preparation method of given compound from cyclopentene is to be stated.

Concept introduction:

Cyclic alkenes on reaction with N-Bromosuccinimide (NBS) forms allyl or benzyl bromide, that is, bromine is substituted at the allylic or benzylic position. NBS is a rich source of free radical of $\text{Br}$. The mechanism followed by NBS is a radical substitution reaction.

Answer to Problem 17.28AP

The preparation method of given compound from cyclopentene is shown below.

Explanation of Solution

Cyclopentene is first brominated and then on treatment with Grignard reagent and epoxide it gives corresponding alkyl alcohol. This alkyl alcohol is oxidized with mild reagent PCC to convert it into aldehyde. Any other reagent will oxidize the alcoholic group to acidic group.

The corresponding reaction sequences to obtain the desired product are shown below.

Figure 4

Conclusion

The preparation method of given compound from cyclopentene is shown in Figure 4.

Interpretation Introduction

(e)

Interpretation:

The preparation method of $3-$ nitro benzoic acid from cumene (isopropyl benzene) is to be stated.

Concept introduction:

The chemical reaction in which an electrophile group is replaced by another functional group is called the electrophilic substitution reaction. When the electrophilic substitution happens on an aromatic ring such as benzene then the reaction is known as electrophilic aromatic substitution.

Answer to Problem 17.28AP

The preparation method of $3-$ nitro benzoic acid from cumene (isopropyl benzene) is shown below.

Explanation of Solution

Cumene has to be oxidized first and then its nitration is done to get the required product

Alkyl group is oxidized to gives benzoic acid. This benzoic acid is nitrated with ${\text{HNO}}_3$ to obtain $3-$ nitro benzoic acid.

The corresponding reaction sequences to obtain the desired product are shown below.

Figure 5

Conclusion

The preparation method of $3-$ nitro benzoic acid from cumene (isopropyl benzene) is shown in Figure 5.

Interpretation Introduction

(f)

Interpretation:

The preparation method of para-nitro benzoic acid from cumene (isopropyl benzene) is to be stated.

Concept introduction:

The chemical reaction in which an electrophile group is replaced by another functional group is known as the electrophilic substitution reaction. When the electrophilic substitution happens on an aromatic ring such as benzene then the reaction is known as electrophilic aromatic substitution.

Answer to Problem 17.28AP

The preparation method of para-nitro benzoic acid from cumene (isopropyl benzene) is shown below.

Explanation of Solution

As alkyl group is ortho and para directing, so, both the derivatives are formed. The reaction of cumene with nitric acid results in the formation of ortho and para nitro-cumene. The para nitro cumene is further oxidized to p-nitro benzoic acid with potassium permangnate.

The corresponding reaction sequences to obtain the desired product are shown below.

Figure 6

Conclusion

The preparation method of para-nitro benzoic acid from cumene (isopropyl benzene) is shown in Figure 6.

Interpretation Introduction

(g)

Interpretation:

The preparation method of $1,2-\text{dimethoxy}-4-\text{benzaldehyde}$ from $1,2-\text{dimethoxy}-4-\text{methylbenzene}$ is to be stated.

Concept introduction:

Cyclic alkenes on reaction with N-Bromosuccinimide (NBS) forms allyl or benzyl bromide, that is, bromine is substituted at the allylic or benzylic position. NBS is a rich source of free radical of $\text{Br}$. The mechanism followed by NBS is a radical substitution reaction.

Answer to Problem 17.28AP

The preparation method of $1,2-\text{dimethoxy}-4-\text{benzaldehyde}$ from $1,2-\text{dimethoxy}-4-\text{methylbenzene}$ is shown below.

Explanation of Solution

In the given reaction, at first, the substrate, $1,2-\text{dimethoxy}-4-\text{methylbenzene}$ is brominated with NBS and then converted to Grignard reagent by the reaction of Mg in ether. This is further hydrolyzed to produce alcohol which is oxidized with mild oxidizing agent PCC to convert it to required aldehyde.

The corresponding reaction sequences to obtain the desired product are shown below.

Figure 7

Conclusion

The preparation method of $1,2-\text{dimethoxy}-4-\text{benzaldehyde}$ from $1,2-\text{dimethoxy}-4-\text{methylbenzene}$ is shown in Figure 7.

Interpretation Introduction

(h)

Interpretation:

The preparation of given compound from cyclopentenol is to be given.

Concept introduction:

The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as a substitution reaction. In a nucleophilic substitution reaction, nucleophile takes the position of leaving the group by attacking the electron-deficient carbon atom.

Answer to Problem 17.28AP

The preparation of given compound from cyclopentenol is shown below.

Explanation of Solution

The given reaction is a nucleophilic substitution reaction. The nucleophile attacks to replace the ${\text{OH}}^{-}$ group. This is a single step reaction therefore a ${\text{S}}_{\text{N}}2$ reaction.

This is a single step substitution nucleophile reaction as shown below.

Figure 8

In this reaction, the stereochemistry of molecule changes as from one side the group is leaving and upon other side of the molecule, nucleophile attacks.

Conclusion

The preparation of given compound from cyclopentenol is shown in Figure 8.