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

9. Alkenes and Alkynes

Alkene Stability

Organic Chemistry

9. Alkenes and Alkynes

Alkene Stability

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1:57 minutes

Problem 15c

Textbook Question

For each set of isomers, choose the isomer that you expect to be most stable and the isomer you expect to be least stable.
(c)

Verified step by step guidance

Analyze the structures of the given isomers. Look for key factors that influence stability, such as the degree of substitution of carbons, resonance stabilization, steric hindrance, and hyperconjugation.

Evaluate the degree of substitution for each isomer. More substituted alkenes (e.g., tertiary > secondary > primary) are generally more stable due to hyperconjugation and inductive effects.

Check for resonance stabilization. Isomers with conjugated systems or resonance structures are typically more stable because delocalization of electrons lowers the overall energy of the molecule.

Assess steric hindrance in each isomer. Isomers with bulky groups in close proximity may experience destabilizing steric interactions, making them less stable.

Rank the isomers based on the above factors to determine which isomer is the most stable and which is the least stable. The most stable isomer will have the optimal combination of substitution, resonance, and minimal steric hindrance, while the least stable isomer will lack these stabilizing features.

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Key Concepts

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

Isomer Stability

Isomer stability refers to the relative energy levels of different isomers, which can be influenced by factors such as steric strain, torsional strain, and electronic effects. Generally, more stable isomers have lower energy due to minimized repulsions and favorable interactions. Understanding the stability of isomers is crucial for predicting their behavior in chemical reactions.

Steric Hindrance

Steric hindrance occurs when atoms or groups within a molecule are forced close together, leading to increased repulsion and instability. In isomers, bulky groups can create steric strain, making certain conformations less favorable. Recognizing steric hindrance helps in determining which isomer might be more or less stable based on the spatial arrangement of substituents.

Torsional Strain

Torsional strain arises from the eclipsing interactions between atoms or groups in a molecule when they are rotated around a bond. This strain is particularly relevant in cyclic compounds and can significantly affect the stability of isomers. Understanding torsional strain allows chemists to predict which conformations of isomers will be more stable based on their rotational barriers.

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Related Practice

Textbook Question

Which species in each pair is more stable?

Textbook Question

Use the data in Table 7-2 to predict the energy difference between 2,3-dimethylbut-1-ene and 2,3-dimethylbut-2-ene. Which of these double-bond isomers is more stable?

Textbook Question

Explain why each of the following alkenes is stable or unstable.

(h)

(i)

Textbook Question

For each set of isomers, choose the isomer that you expect to be most stable and the isomer you expect to be least stable.

(b)

Textbook Question

In 1935, J. Bredt, a German chemist, proposed that a bicycloalkene could not have a double bond at a bridgehead carbon unless one of the rings contains at least eight carbons. This is known as Bredt's rule. Explain why there cannot be a double bond at this position.

Textbook Question

Rank the following compounds from most stable to least stable:

trans-3-hexene, cis-3-hexene, cis-2,5-dimethyl-3-hexene, (Z)-3,4-dimethyl-3-hexene

Textbook Question

The energy difference between cis- and trans-but-2-ene is about 4 kJ/mol; however, the trans isomer of 4,4-dimethylpent-2-ene is nearly 16 kJ/mol more stable than the cis isomer. Explain this large difference.

Textbook Question

For each set of isomers, choose the isomer that you expect to be most stable and the isomer you expect to be least stable.

(a)

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