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

11. Radical Reactions

Allylic Bromination

Organic Chemistry

11. Radical Reactions

Allylic Bromination

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5:17 minutes

Problem 32c

Textbook Question

Predict the products of the following allylic halogenation reactions.
(c)

Verified step by step guidance

Identify the allylic position in the given molecule. The allylic position is the carbon atom adjacent to a carbon-carbon double bond.

Determine the halogen used in the reaction. Allylic halogenation typically involves chlorine (Cl2) or bromine (Br2) in the presence of a radical initiator like N-bromosuccinimide (NBS) for bromination.

Understand the mechanism: Allylic halogenation proceeds via a radical mechanism. The reaction begins with the formation of a radical at the allylic position.

Consider resonance stabilization: The allylic radical can be stabilized by resonance, which means the radical can be delocalized over the π system. Draw all possible resonance structures to identify potential sites for halogenation.

Predict the products: The halogen will add to the allylic position, and due to resonance, multiple products may form. Identify all possible products by considering each resonance structure and where the halogen can add.

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Key Concepts

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

Allylic Halogenation

Allylic halogenation is a reaction where a halogen atom is introduced at the allylic position of an alkene. This position is adjacent to the double bond, and the reaction typically involves the use of N-bromosuccinimide (NBS) in the presence of light or heat to generate radicals. The process is selective for the allylic position due to the stability of the allylic radical intermediate.

Radical Mechanism

The radical mechanism is a chain reaction involving initiation, propagation, and termination steps. In allylic halogenation, the initiation step generates radicals, often through the homolytic cleavage of a halogen molecule. Propagation involves the abstraction of a hydrogen atom from the allylic position, forming a stable allylic radical, which then reacts with a halogen molecule to form the halogenated product and regenerate the radical.

Stability of Allylic Radicals

Allylic radicals are more stable than typical alkyl radicals due to resonance stabilization. The unpaired electron in an allylic radical can be delocalized over the π system of the adjacent double bond, distributing the radical character over multiple atoms. This delocalization lowers the energy of the radical, making allylic positions more reactive in radical halogenation reactions.

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