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

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1:04 minutes

Problem 4c

Textbook Question

Which species in each pair is more stable?
c.

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Analyze the structures of the two species provided. Both species contain an oxygen atom with a negative charge (-O⁻) attached to a carbon chain. The difference lies in the substitution pattern of the alkene group.

Consider the concept of alkene stability. Alkenes are stabilized by hyperconjugation and inductive effects from alkyl groups attached to the double bond. More substituted alkenes are generally more stable due to increased hyperconjugation.

Examine the first species (CH₃CHCH=CH₂). The double bond is monosubstituted, meaning it has only one alkyl group (CH₃) attached to the double bond. This results in lower stability compared to more substituted alkenes.

Examine the second species (CH₃C=CHCH₃). The double bond is disubstituted, meaning it has two alkyl groups (CH₃ and CH₃) attached to the double bond. This increases stability due to greater hyperconjugation and inductive effects.

Conclude that the second species (CH₃C=CHCH₃) is more stable than the first species (CH₃CHCH=CH₂) because the double bond in the second species is more substituted, leading to increased stabilization.

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Key Concepts

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

Stability of Chemical Species

The stability of chemical species refers to their tendency to maintain their structure and resist change. Factors influencing stability include the energy of the species, resonance structures, and steric hindrance. More stable species typically have lower energy and are less reactive, making them less likely to undergo chemical transformations.

Resonance Structures

Resonance structures are different ways of drawing the same molecule that illustrate the delocalization of electrons. A molecule with multiple resonance forms can distribute its electron density more evenly, leading to increased stability. The actual structure of the molecule is a hybrid of these forms, and the more resonance forms a species has, the more stable it generally is.

Steric Hindrance

Steric hindrance occurs when atoms within a molecule are forced into close proximity, leading to repulsive interactions that can destabilize the structure. Larger groups or substituents can create steric strain, making a molecule less stable. Understanding steric effects is crucial for predicting the stability of different species, especially in organic compounds.

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Related Practice

Textbook Question

The benzene ring alters the reactivity of a neighboring group in the benzylic position much as a double bond alters the reactivity of groups in the allylic position.

Benzylic cations, anions, and radicals are all more stable than simple alkyl intermediates.

a. Use resonance forms to show the delocalization (over four carbon atoms) of the positive charge of the benzyl cation.

Textbook Question

The benzene ring alters the reactivity of a neighboring group in the benzylic position much as a double bond alters the reactivity of groups in the allylic position.

Benzylic cations, anions, and radicals are all more stable than simple alkyl intermediates.

a. Use resonance forms to show the delocalization (over four carbon atoms) of the unpaired electron of the benzyl radical.

Textbook Question

The benzene ring alters the reactivity of a neighboring group in the benzylic position much as a double bond alters the reactivity of groups in the allylic position.

Benzylic cations, anions, and radicals are all more stable than simple alkyl intermediates.

c. Which of the following reactions will have the faster rate and give the better yield? Use a drawing of the transition state to explain your answer.

Textbook Question

Which species in each pair is more stable?

Textbook Question

Which species in each pair is more stable?

Textbook Question

Which species in each pair is more stable?

Textbook Question

Name the following dienes and rank them from most stable to least stable.

Textbook Question

Which compound would you expect to have the greater heat of hydrogenation: 1,2-pentadiene or 1,4-pentadiene?

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