Chapter 6, Problem 53P

Interpretation Introduction

(a)

Interpretation: The curved arrows are to be used to show the conversion of A and B to C.

Concept introduction: The Diels-Alder reactions are the chemical reactions in which diene and dienophile participate to form Diels-Alder adduct. The diene compounds should be conjugated. Conjugated compounds contain at least one single bond in between two double bonds.

Curved arrows aid in determining the movement and flow of electrons in the reaction. The electrons that take part in the chemical reactions are shown by the curved arrows. An electronegative element in the reaction attracts electron toward it.

Half headed arrows are used to show the flow of single electrons, while the full headed arrow shows the movement of electron pairs.

Interpretation Introduction

(b)

Interpretation: The bonds that are broken and formed in the given reaction are to be identified.

Concept introduction: The bonds in the reactions are broken to form the new compounds. During the formation of products, new bonds are formed. The sum of bonds broken and bonds formed in the reactions are used to calculate the enthalpy change in the reaction.

Interpretation Introduction

(c)

Interpretation: The reaction is endothermic or exothermic is to be identified.

Concept introduction: The chemical reaction in which energy is released during the formation of products is known as exothermic reactions. The energy released during the reaction is denoted by $\text{ΔH°}$. Exothermic and endothermic reactions are opposite to each other.

Interpretation Introduction

(d)

Interpretation: Entropy favors the reactants or products are to be identified.

Concept introduction: The change in Gibbs free energy, enthalpy and entropy is represented by $\Delta G°$, $\text{Δ}H\text{°}$ and $\text{Δ}S\text{°}$ respectively. They are state functions. The relation of $\Delta G°$, $\text{Δ}H\text{°}$ and $\text{Δ}S\text{°}$ is shown as,

$\text{Δ}G\text{°}=\text{Δ}H\text{°}-T\text{Δ}S\text{°}$

The change in Gibbs free energy describes the spontaneity of the reaction. The change in enthalpy describes the relative bond strength in the substance, whereas the change in entropy describes the randomness in the system.

Interpretation Introduction

(e)

Interpretation: The Diels-Alder reaction is to be classified as a substitution, elimination, or addition reaction.

Concept introduction: The substitution reactions involve the substitution or replacement of an atom or group of atoms in a compound by anotheratom or groups of atoms. In the substitution reactions, the replacement takes place by the break down of sigma bonds.

In elimination reaction, the formation of $\text{π}$ bonds occurs due to the removal of an atom or group of atoms from the starting material, whereas the addition reaction involves the addition of elements into the starting material.