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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5:41 minutes

Problem 32a

Textbook Question

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

Verified step by step guidance

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

Recognize that allylic halogenation typically involves the substitution of a hydrogen atom at the allylic position with a halogen atom, often using reagents like N-bromosuccinimide (NBS) in the presence of light or heat.

Consider the resonance stabilization of the allylic radical formed during the reaction. The allylic radical can delocalize its unpaired electron over the π system, leading to multiple resonance structures.

Determine the most stable resonance structure of the allylic radical, as this will guide the formation of the major product. The stability is often influenced by the degree of substitution at the allylic position.

Predict the final product by replacing the hydrogen atom at the allylic position with the halogen atom, taking into account the most stable resonance structure and the regioselectivity of the reaction.

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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 a carbon-carbon double bond. The reaction typically involves the use of N-bromosuccinimide (NBS) in the presence of light or heat, which generates a radical that abstracts a hydrogen atom from the allylic position, allowing the halogen to attach there.

Radical Mechanism

The radical mechanism is a chain reaction process 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 radical reacting with the substrate to form a new radical, which continues the chain reaction. Understanding this mechanism is crucial for predicting the products formed during the reaction.

Resonance Stabilization

Resonance stabilization is a concept where the stability of a molecule is increased due to the delocalization of electrons across multiple atoms. In allylic systems, the allylic radical formed during halogenation is stabilized by resonance, as the unpaired electron can be delocalized over the π system. This stabilization influences the regioselectivity of the reaction, often leading to multiple possible products depending on the structure of the starting material.

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