Chapter 15, Problem 15.43AP

Interpretation Introduction

(a)

Interpretation:

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with ${\text{Br}}_{\text{2}}$ (dark) in ${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$ is to be stated.

Concept introduction:

Conjugated dienes are defined as two double bonds separated by one single bond. They are more stable than non-conjugated double bonds due to resonance and hybridization energy. Along with that the heat of hydrogenation effects the stability of conjugated dienes. It states that higher the heat of hydrogenation energy lowers the stability of dienes.

Answer to Problem 15.43AP

The complete reaction is written as shown below.

Explanation of Solution

When $trans-1,3-\text{pentadiene}$ reacts with ${\text{Br}}_{\text{2}}$ (dark) in ${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$, it gives $1,2-$ and $1,4-$ addition product. In presence of heat, this reaction gives $1,2-$ addition major product which is $\left(E\right)-4,5-\text{dibromopent}-2-\text{ene}$. The complete reaction is written as shown below.

Figure 1

Conclusion

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with ${\text{Br}}_{\text{2}}$ (dark) in ${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$ is $\left(E\right)-4,5-\text{dibromopent}-2-\text{ene}$ (major) and $\left(E\right)-1,4-\text{dibromopent}-2-\text{ene}$ (minor).

Interpretation Introduction

(b)

Interpretation:

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with $\text{HBr}$ is to be stated.

Concept introduction:

Conjugated dienes areb defined as two double bonds separated by one single bond. They are more stable than non-conjugated double bonds due to resonance and hybridization energy. Along with that the heat of hydrogenation effects the stability of conjugated dienes. It states that higher the heat of hydrogenation energy lowers the stability of dienes.

Answer to Problem 15.43AP

The complete reaction is written as shown below.

Explanation of Solution

When $trans-1,3-\text{pentadiene}$ reacts with $\text{HBr}$ gives $1,2-$ addition only product which is $\left(E\right)-4-\text{bromopent}-2-\text{ene}$. The complete reaction is written as shown below.

Figure 2

Conclusion

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with $\text{HBr}$ is $\left(E\right)-4-\text{bromopent}-2-\text{ene}$.

Interpretation Introduction

(c)

Interpretation:

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with ${\text{H}}_{\text{2}}$ (two molar equivalents) is to be stated.

Concept introduction:

Conjugated dienes are defined as two double bonds separated by one single bond. They are more stable than non-conjugated double bonds due to resonance and hybridization energy. Along with that the heat of hydrogenation effects the stability of conjugated dienes. It states that higher the heat of hydrogenation energy lowers the stability of dienes.

Answer to Problem 15.43AP

The complete reaction is written as shown below.

Explanation of Solution

When $trans-1,3-\text{pentadiene}$ reacts with ${\text{H}}_{\text{2}}$ (two molar equivalents). It undergoes hydrogenation reaction which result in the formation of pentane. The reaction is written as shown below.

Figure 3

Conclusion

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with ${\text{H}}_{\text{2}}$ (two molar equivalents) is pentane.

Interpretation Introduction

(d)

Interpretation:

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{3}}{\text{O}}^{+}$ is to be stated.

Concept introduction:

Conjugated dienes are defined as two double bonds separated by one single bond. They are more stable than non-conjugated double bonds due to resonance and hybridization energy. Along with that the heat of hydrogenation effects the stability of conjugated dienes. It states that higher the heat of hydrogenation energy lowers the stability of dienes.

Answer to Problem 15.43AP

The complete reaction is written as shown below.

Explanation of Solution

When $trans-1,3-\text{pentadiene}$ reacts with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{3}}{\text{O}}^{+}$ it gives $\left(E\right)-\text{pent}-3-\text{en}-2-\text{ol}$. The chemical reaction is written as shown below.

Figure 4

Conclusion

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_{\text{3}}{\text{O}}^{+}$ is $\left(E\right)-\text{pent}-3-\text{en}-2-\text{ol}$.

Interpretation Introduction

(e)

Interpretation:

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with ${\text{Na}}^{\text{+}}{\text{EtO}}^{-}$ in $\text{EtOH}$ is to be stated.

Concept introduction:

Conjugated dienes are defined as two double bonds separated by one single bond. They are more stable than non-conjugated double bonds due to resonance and hybridization energy. Along with that the heat of hydrogenation effects the stability of conjugated dienes. It states that higher the heat of hydrogenation energy lowers the stability of dienes.

Answer to Problem 15.43AP

The reaction does not undergo any chemical change because alkenes do not undergo any nucleophilic addition reaction.

Explanation of Solution

When $trans-1,3-\text{pentadiene}$ reacts with ${\text{Na}}^{\text{+}}{\text{EtO}}^{-}$ in $\text{EtOH}$. It does not give any product because alkenes do not undergo any nucleophilic addition reaction. It is due to repulsion between the negative charge of nucleophile and $\text{π}$ electron cloud of alkene. Therefore, no reaction take place.

Conclusion

Alkenes do not undergo any nucleophilic addition reaction it means no product is formed in this reaction.

Interpretation Introduction

(f)

Interpretation:

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with maleic anhydride and heat is to be stated.

Concept introduction:

A chemical reaction that involves cycloaddition is known as Diels-Alder reaction. The reactant molecules that give rise to the product are diene and dienophile. The rate of reaction is fast when the electronegative group is attached to dienophile. In this type of reaction, syn addition takes place.

Answer to Problem 15.43AP

The complete reaction is written below.

Explanation of Solution

When $trans-1,3-\text{pentadiene}$ reacts with maleic anhydride in presence of heat it gives a Diels-Alder adduct. The complete reaction is written as shown below.

Figure 5

Conclusion

The product obtained on reaction of $trans-1,3-\text{pentadiene}$ with maleic anhydride, heat is Diels-Alder adduct as shown in Figure 5.