Chapter 20, Problem 20.36P

Interpretation Introduction

Interpretation: In the given intramolecular Diels-Alder reaction, the structural formula of the product has to be predicted.

Concept Introduction:

Diels-Alder reaction:

It is the reaction of conjugated dienes with double or triple bonded compounds which are known as “dienophiles”. The reaction is a $4+2$ cycloaddition reaction that results in the formation of a six membered cyclic product which is known as “adduct”.

Example:

This mechanism shown that three $\text{π}$-bonds are broken to form two new $\text{σ}$ -bonds and a new $\text{π}$-bond.

Diels-Alder reaction to form bicyclic system:

The Diels-Alder adduct formed in the Diels-Alder reaction can also be a bicyclic system which will be obtained when cylopentadiene is used as the diene as shown here:

In this reaction, the cylopentadiene acts as both diene and dienophile and formed a bicyclic system. When it is heated to ${\text{170}}^{\text{o}}\text{C}$, a reverse Diels-Alder reaction takes place in which the bicyclic system will be decomposed and gives back the cylopentadiene.

Intramolecular reaction:

In the word “Intramolecular”- “Intra”- means “within” or “in”. So an intramolecular reaction means the reaction is taking place within one molecule itself without the involvement of any other molecules.