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

16. Conjugated Systems

Stability of Conjugated Intermediates

Organic Chemistry

16. Conjugated Systems

Stability of Conjugated Intermediates

Previous problemNext problem

Problem 54b

Textbook Question

Which of the following reactions would you expect to be faster/more favorable in each pair? Why?
(b)

Verified step by step guidance

Identify the type of reaction: Both reactions involve the abstraction of a hydrogen atom by a bromine radical (Br•) from a cyclohexane derivative, leading to the formation of a cyclohexyl radical.

Analyze the stability of the radicals formed: In the first reaction, the radical is formed on a saturated cyclohexane ring, while in the second reaction, the radical is formed on a cyclohexene ring, which has an alkene group.

Consider the effect of the alkene: The presence of the alkene in the cyclohexene can stabilize the radical through hyperconjugation and resonance, making the radical more stable compared to the radical formed in the saturated cyclohexane.

Evaluate the reaction rate: Reactions that form more stable intermediates (radicals, in this case) are generally faster and more favorable. Therefore, the reaction involving the cyclohexene is expected to be faster due to the additional stabilization of the radical.

Conclude which reaction is faster: Based on the stability of the radicals, the reaction involving the cyclohexene is more favorable and faster than the reaction involving the saturated cyclohexane.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Play a video:

Was this helpful?

Key Concepts

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

Radical Stability

Radical stability is crucial in determining the rate of radical reactions. More stable radicals form faster and are more favorable. Stability is influenced by factors like hyperconjugation and resonance. In the image, the radical formed in the second reaction is stabilized by the adjacent double bond, making it more favorable.

Bromine Radical Reactivity

Bromine radicals are highly reactive species that can abstract hydrogen atoms from organic molecules, forming new radicals. The reactivity of bromine radicals is influenced by the stability of the resulting radical. In the image, the bromine radical reacts with cyclohexane and cyclohexene, with the latter being more favorable due to radical stabilization.

Allylic Position

The allylic position refers to the carbon atom adjacent to a double bond. Radicals formed at allylic positions are more stable due to resonance stabilization, which allows the radical to be delocalized over the π system. In the image, the second reaction involves an allylic radical, making it faster and more favorable compared to the first reaction.

Watch next

Master Stability of Conjugated Intermediates with a bite sized video explanation from Johnny

Start learning