Question

In Solved Problem 15-2, we simply predicted that the products would have a 1, 2-or 1, 4-relationship of the proper substitutents. Draw the charge-separated resonance forms of the reactants to support these predictions.

Short answer

Diels-Alder reactions are important in photochemistry.Alkenes and alkynes comprising electron-withdrawing groups incorporate to conjugated dienes to generate six-membered rings.

Step-by-step solution

Diels-Alder reaction

Diels-Alder reactions are important in photochemistry.Alkenes and alkynes comprising electron-withdrawing groups incorporate to conjugated dienes to generate six-membered rings.

Diels-Alder reactions using unsymmetrical reagents

Diels-Alder reactions generate single products and not a mixture even in cases where the diene and dienophile comprise unsymmetrical substitution. The major product can be predicted by observing how the substitutents polarize the diene and dienophile charge resonated forms.

Charge separated resonance forms of the structures

The first reaction in the solved problem a is given as:

First reaction in solved problem a

The given reaction happens between isoprene and but-3-en-2-one to produce the product. The charge separated resonance denotes the separation of positive and negative charge on the molecule. The charge separated resonance forms of the reactant can be given as:

Charge separated resonance forms of reaction a

The second reaction in problem 15-2 is given as:

Second reaction in problem 15-2

The given reaction happens between acrylonitrile and (E)-1-,methoxybuta-1,3-diene to produce the product. The charge separated resonance forms of the product are given as:

Charge separated resonance forms of the reactant b