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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2:15 minutes

Problem 18a

Textbook Question

Two products are formed when methylenecyclohexane reacts with NBS? Show how each is formed. Disregard stereoisomers.

Verified step by step guidance

Step 1: Recognize that NBS (N-Bromosuccinimide) is used for allylic bromination. This reaction occurs in the presence of heat (Δ) and a radical initiator like peroxide, which generates bromine radicals.

Step 2: Identify the allylic position in methylenecyclohexane. The allylic position is the carbon atom adjacent to the double bond, which is more reactive due to resonance stabilization of the resulting radical.

Step 3: Generate a bromine radical from NBS. The bromine radical abstracts a hydrogen atom from the allylic position of methylenecyclohexane, forming an allylic radical.

Step 4: The allylic radical undergoes resonance stabilization, creating two possible resonance structures. These resonance structures correspond to two different positions where bromine can add.

Step 5: Bromine from NBS reacts with the allylic radical at each resonance structure, forming two products: (1) 1-bromo-3-methylenecyclohexane and (2) 3-bromo-1-methylenecyclohexane. Disregard stereoisomers as specified in the problem.

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Key Concepts

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

Radical Bromination

Radical bromination is a reaction where bromine (Br2) is used to add bromine atoms to an alkene or alkane through a radical mechanism. In the presence of light or heat, Br2 dissociates into two bromine radicals, which can then react with the double bond of methylenecyclohexane, leading to the formation of brominated products. This process is crucial for understanding how N-bromosuccinimide (NBS) facilitates bromination in organic reactions.

Mechanism of Electrophilic Addition

The mechanism of electrophilic addition involves the attack of an electrophile on a nucleophilic site, typically a double bond in alkenes. In the case of methylenecyclohexane reacting with NBS, the double bond acts as a nucleophile, allowing the bromine radical to add across the double bond, resulting in the formation of two distinct products. Understanding this mechanism is essential for predicting the products formed in the reaction.

Regioselectivity

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others when multiple products are possible. In the reaction of methylenecyclohexane with NBS, the formation of different brominated products can occur at various positions on the cyclohexane ring. Recognizing the regioselectivity helps in determining which products are likely to be formed based on the stability of the resulting radicals and the structure of the starting material.

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