Chapter 16, Problem 46PP

Interpretation Introduction

Interpretation:

The trend of reactivity for Cyclopentadiene, 1,3-cyclohexadiene and 1,3-cycloheptadiene are rapidly reactive, mild reactive and unreactive respectively in Diels-Alder reaction should be explained.

Concept introduction:

• Cycloaddition reaction is a concerted addition reaction of two reactants to form a ring; in which two π-bonds are converted to two σ-bonds.
• Diels-Alder reaction is a $\left[\text{4+2}\right]\text{ cycloaddition}$ reaction, in which a π-system having four atoms (diene) and a π-system having two atoms (dienophile) are undergoing in cycloaddition reaction and producing a substituted cyclohexene.
• The mechanism of the ring formation in the Diels-Alder reaction is drawn by using three arrows representing the shifting of π-bonds in the two π-systems in a clockwise or counter clockwise fashion, so that the ring formation will take place.
• The more steric hindrance in the dienes will be less reactive for the Diels-Alder reaction.