Chapter 24, Problem 24.8YT

Interpretation Introduction

Interpretation:

In the Diels-Alder reaction, which interaction out of A and B leads to form the major product is to be explained.

Concept introduction:

Diels-Alder reactions are concerted and stereospecific. When the diene and the dienophile of a Diels–Alder reaction are both unsymmetric, the major isomeric product is the one produced by the approach that exhibits the more favorable electrostatic attraction among atoms undergoing bond formation. The oppositely charged species are attracted by each other, while there is a repulsive interaction between the same charged species. Therefore, the regiochemistry in Diels-Alder reaction depends on the nature of substituents on diene as well as that on dienophile. An electron-donating substituent on the diene and an electron-withdrawing substituent on the dienophile not only enhance the rate of given Diels-Alder reaction but also decide which isomer will form predominantly and the stereochemistry as well.