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

19. Reactions of Aromatics: EAS and Beyond

Side-Chain Halogenation

Organic Chemistry

19. Reactions of Aromatics: EAS and Beyond

Side-Chain Halogenation

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3:44 minutes

Problem 63b

Textbook Question

Predict the product of the following benzylic bromination reactions.
(b)

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Identify the type of reaction: This is a benzylic bromination reaction, which typically involves the substitution of a hydrogen atom at the benzylic position with a bromine atom.

Locate the benzylic position: The benzylic position is the carbon atom directly attached to the benzene ring. In this reaction, identify the carbon atom that is adjacent to the benzene ring.

Consider the mechanism: Benzylic bromination usually proceeds via a radical mechanism. The presence of a radical initiator, such as N-bromosuccinimide (NBS), facilitates the formation of a benzylic radical.

Predict the formation of the benzylic radical: The hydrogen atom at the benzylic position is abstracted, forming a benzylic radical. This radical is stabilized by resonance with the benzene ring.

Determine the final product: The benzylic radical reacts with bromine to form the brominated product. The bromine atom replaces the hydrogen atom at the benzylic position, resulting in the formation of the benzylic bromide.

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Key Concepts

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

Benzylic Bromination

Benzylic bromination is a type of radical halogenation reaction where a bromine atom is introduced at the benzylic position, which is the carbon atom directly attached to a benzene ring. This reaction typically involves the use of N-bromosuccinimide (NBS) and a radical initiator, such as light or heat, to generate bromine radicals that selectively react with the benzylic hydrogen atoms.

Radical Mechanism

Radical mechanisms involve the formation and reaction of radicals, which are species with unpaired electrons. In benzylic bromination, the reaction proceeds through a radical chain mechanism, starting with the generation of bromine radicals, followed by hydrogen abstraction from the benzylic position, and finally, the formation of the brominated product. Understanding the stability and reactivity of radicals is crucial for predicting the outcome of such reactions.

Benzylic Position Stability

The benzylic position is highly reactive due to the stability of the benzylic radical formed during the reaction. This stability arises from resonance, where the unpaired electron can be delocalized over the aromatic ring, making the benzylic radical more stable than other alkyl radicals. This enhanced stability is a key factor in the selectivity of benzylic bromination reactions, as it favors the formation of products at the benzylic position.

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