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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3:26 minutes

Problem 47c

Textbook Question

Predict the major product(s) of the following allylic bromination 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 double bond.

Understand that allylic bromination involves the substitution of a hydrogen atom at the allylic position with a bromine atom, typically using 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 the unpaired electron over the π system, leading to multiple resonance structures.

Determine the most stable resonance structure, which will guide you to predict the major product. The stability is often influenced by the degree of substitution of the radical and the overall stability of the resulting product.

Predict the major product by substituting the bromine atom at the most stable allylic position, considering the resonance structures and the stability of the resulting brominated compound.

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Key Concepts

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

Allylic Bromination

Allylic bromination is a type of radical substitution reaction where a bromine 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 bromine radicals that facilitate the substitution.

Radical Mechanism

The radical mechanism is crucial for understanding allylic bromination. It involves the formation of a bromine radical, which abstracts a hydrogen atom from the allylic position, creating an allylic radical. This radical then reacts with another bromine molecule to form the brominated product. The stability of the allylic radical is key to predicting the major product.

Regioselectivity in Allylic Bromination

Regioselectivity refers to the preference for the formation of one constitutional isomer over others in a chemical reaction. In allylic bromination, the most stable allylic radical is formed preferentially, leading to the major product. Factors such as resonance stabilization and steric effects influence which allylic position is brominated, guiding the prediction of the major product.

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Related Practice

Textbook Question

The light-initiated reaction of 2,3-dimethylbut-2-ene with N-bromosuccinimide (NBS) gives two products:

a. Give a mechanism for this reaction, showing how the two products arise as a consequence of the resonance-stabilized intermediate.

Textbook Question

The light-initiated reaction of 2,3-dimethylbut-2-ene with N-bromosuccinimide (NBS) gives two products:

b. The bromination of cyclohexene using NBS gives only one major product, as shown on the previous page. Explain why there is no second product from an allylic shift.

Textbook Question

Using 1,2-dimethylcyclohexene as your starting material, show how you would synthesize the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.) If a chiral product is shown, assume that it is part of a racemic mixture.

(a)

Textbook Question

Predict the major product(s) of the following allylic bromination reactions.

(a)

Textbook Question

Suggest a mechanism for the following reactions.

(c)

Textbook Question

Identify the two different alkenes that undergo allylic halogenation to prepare the compound shown.

Textbook Question

In the following molecules, identify the carbon where the radical is most likely to form in the first propagation step.

(c)

Textbook Question

In the following molecules, identify the carbon where the radical is most likely to form in the first propagation step.

(d)

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Predict the major product(s) of the following allylic bromination reactions. (c)

Key Concepts

Allylic Bromination

Radical Mechanism

Regioselectivity in Allylic Bromination

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Predict the major product(s) of the following allylic bromination reactions.
(c)