Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

16. Conjugated Systems

Diels-Alder Reaction

Organic Chemistry

16. Conjugated Systems

Diels-Alder Reaction

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Problem 14

Textbook Question

Figure 22.16(a) <IMAGE> shows a unique example where the Diels–Alder reaction gives a single product (no enantiomers) regardless of whether the diene attacks the dienophile from the top or bottom.
(a) Show the product of the diene attacking from the bottom and confirm that the same product is obtained.
(b) What is special about this product that makes this true?

Verified step by step guidance

Identify the diene and dienophile involved in the Diels–Alder reaction. The diene is a conjugated system with two double bonds, and the dienophile is typically an alkene or alkyne with electron-withdrawing groups.

Draw the diene and dienophile in their correct orientations. For the diene, ensure that the p orbitals are aligned to allow for the formation of new sigma bonds. For the dienophile, position it so that it can interact with the diene.

Consider the approach of the diene to the dienophile from the bottom. In a Diels–Alder reaction, the diene and dienophile undergo a concerted cycloaddition to form a six-membered ring. Draw the transition state where the new sigma bonds are forming.

Complete the cycloaddition by forming the new sigma bonds between the diene and dienophile. This will result in a cyclohexene ring. Ensure that the stereochemistry is consistent with the approach from the bottom.

Analyze the product to determine why it is unique. The product is likely symmetrical or has a plane of symmetry, which results in the same product regardless of the approach direction. This symmetry prevents the formation of enantiomers, leading to a single product.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Diels–Alder Reaction

The Diels–Alder reaction is a [4+2] cycloaddition between a conjugated diene and a dienophile, forming a six-membered ring. It is a pericyclic reaction that proceeds via a concerted mechanism, often used to synthesize complex cyclic structures. Understanding the stereochemistry and regiochemistry of the reactants is crucial for predicting the product.

Stereochemistry

Stereochemistry involves the study of the spatial arrangement of atoms in molecules and its impact on chemical reactions. In the Diels–Alder reaction, the orientation of the diene and dienophile can lead to different stereoisomers. However, certain symmetrical or constrained systems can lead to a single stereochemical outcome, as seen in the given example.

Symmetry in Organic Molecules

Symmetry in organic molecules can lead to unique chemical behavior, such as producing a single product in reactions that typically yield multiple stereoisomers. In the context of the Diels–Alder reaction, symmetry in the diene or dienophile can result in identical products regardless of the approach direction, due to equivalent spatial arrangements.

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Related Practice

Textbook Question

Predict the product of the Diels–Alder reactions shown.

(a)

Textbook Question

While not covered explicitly in this chapter, the ene reaction occurs similarly to the Diels–Alder reaction but replaces the electrons from one bond in the diene with the electrons in a C―H bond. Draw the mechanism for the following reaction. [Number the carbons and draw in the hydrogens of the product. And, of course, make a note of bonds formed and bonds broken.]

Textbook Question

Diene A participates in a fast and efficient Diels–Alder reaction with maleic anhydride, the powerful dienophile from Assessment 22.9. However, the related diene B does not undergo a Diels–Alder reaction. Why?

Textbook Question

Predict the product of the following Diels–Alder reactions. Where a racemic mixture is produced, show both enantiomers and explain how each is formed.

(d)

Textbook Question

Assuming the diene approaches the dienophile from the top, predict the product of the following Diels–Alder reactions.

(c)

Textbook Question

In each Diels–Alder reaction shown, predict the product that will result.(a)

Textbook Question

In each Diels–Alder reaction shown, predict the product that will result.

(c)

Textbook Question

Predict the product of the following reactions. [When all of the reactions from this chapter are shown together, you must first decide which type of reaction each is. Is it a Diels–Alder, an electrocyclic, or a sigmatropic rearrangement? Drawing the product will be easier once this determination is made.]

(a)

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