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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4:53 minutes

Problem 19

Textbook Question

How many allylic substituted bromoalkenes are formed from the reactions in Problems 17 if stereoisomers are included?

Verified step by step guidance

Step 1: Analyze the given reaction conditions. The reaction involves NBS (N-bromosuccinimide) in the presence of heat (Δ) and peroxide. This is a radical bromination reaction that selectively brominates allylic positions in alkenes.

Step 2: Identify the allylic positions in the given molecule. Allylic positions are the carbon atoms adjacent to the double bond. In the provided structure, there are two allylic positions on either side of the double bond.

Step 3: Consider the possible products formed by bromination at each allylic position. Bromination at each allylic position can lead to different regioisomers, depending on which allylic hydrogen is replaced by bromine.

Step 4: Account for stereoisomers. Since the allylic carbons are sp3 hybridized, bromination can lead to stereoisomers (R and S configurations) at each brominated position. This increases the number of possible products.

Step 5: Combine regioisomeric and stereoisomeric possibilities. For each allylic position, consider the number of stereoisomers formed. Add these together to determine the total number of allylic substituted bromoalkenes formed.

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Key Concepts

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

Allylic Substitution

Allylic substitution refers to the replacement of a hydrogen atom at the allylic position (the carbon adjacent to a double bond) with another atom or group. This reaction is significant in organic chemistry as it allows for the formation of new compounds with varied properties. The presence of a double bond influences the reactivity and stability of the intermediates formed during the reaction.

Bromination with NBS

N-Bromosuccinimide (NBS) is a reagent commonly used for allylic bromination. It generates bromine radicals under specific conditions, such as heat or light, which can abstract hydrogen atoms from the allylic position, leading to the formation of allylic bromides. This method is advantageous because it selectively brominates the allylic position while minimizing the formation of other byproducts.

Stereoisomerism

Stereoisomerism occurs when compounds have the same molecular formula and connectivity but differ in the spatial arrangement of their atoms. In the context of allylic bromination, the formation of stereoisomers is crucial as different configurations (cis/trans or E/Z) can arise from the reaction. Understanding stereoisomerism is essential for predicting the number of distinct products formed in a reaction, especially when multiple chiral centers are involved.

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