Chapter 24, Problem 24.13P

Interpretation Introduction

Interpretation:

The product is produced from a Diels-Alder reaction of ethene and diene. The structure of the diene that required for the reaction is to be identified.

Concept introduction:

The $\left[\text{4+2}\right]$ cycloaddition reactions are generally known as a Diels-Alder reaction. In this reaction, a conjugated diene and a dienophile are joined via the formation of two new sigma bonds. The product is a six-membered ring. For a Diels-Alder reaction to proceed, the diene essential be able to achieve the s-cis conformation. Diels-Alder reactions cannot take place with the diene in the s-trans conformation. Electron-donating substituents bonded directly to the diene carbons and electron-withdrawing substituents bonded directly to the dienophile carbons facilitate standard Diels–Alder reactions. These reactions are stereospecific. The stereochemistry of the reactants forecasts the stereochemistry of the product. If the $\text{C=C}$ bonds in the diene are either both cis or both trans, then the substituents on the products are cis to each other. If one of the diene’s double bonds is trans and the other is cis, then substituents attached to the products are trans to each other.