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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3:22 minutes

Problem 86f

Textbook Question

Which species in each pair is more stable?
f.

Verified step by step guidance

Step 1: Understand the concept of stability in organic chemistry. Stability can be influenced by factors such as resonance, inductive effects, hyperconjugation, steric hindrance, and aromaticity. These factors help determine which species in a pair is more stable.

Step 2: Analyze the electronic structure of each species in the pair. Look for resonance structures, as delocalization of electrons typically increases stability. Use resonance rules to determine if one species has more resonance contributors than the other.

Step 3: Evaluate the inductive effects. Electronegative atoms or groups attached to the molecule can withdraw electron density through sigma bonds, stabilizing the molecule. Compare the presence and position of electronegative groups in each species.

Step 4: Consider hyperconjugation. If one species has more alkyl groups attached to a positively charged carbon or a double bond, it may be stabilized by hyperconjugation. Count the number of hyperconjugative interactions in each species.

Step 5: Check for steric hindrance and aromaticity. Steric hindrance can destabilize a molecule if bulky groups are too close together. Aromatic species are highly stable due to delocalized π-electrons following Huckel's rule (4n+2 π-electrons). Determine if either species is aromatic or suffers from steric hindrance.

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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 bond strength, molecular geometry, and the presence of electron-withdrawing or donating groups. More stable species typically have lower energy configurations 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 structures can distribute its electron density more evenly, leading to increased stability. The actual structure of the molecule is a hybrid of these resonance forms, and the more resonance forms a species has, the more stable it generally is.

Electronegativity and Inductive Effects

Electronegativity is the ability of an atom to attract electrons in a bond. Atoms with high electronegativity can stabilize negative charges through inductive effects, where they pull electron density towards themselves. This can enhance the stability of a species, especially in the presence of electronegative atoms or groups that can help distribute charge or stabilize reactive intermediates.

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Related Practice

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)

Textbook Question

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

(a) 1,2-dimethylcyclopentene

(b) trans-1,2-dimethylcyclopentene

(d) trans-1,2-dimethylcyclodecene

Textbook Question

A double bond in a six-membered ring is usually more stable in an endocyclic position than in an exocyclic position. Hydrogenation data on two pairs of compounds follow. One pair suggests that the energy difference between endocyclic and exocyclic double bonds is about 9 kJ/mol. The other pair suggests an energy difference of about 5 kJ/mol. Which number do you trust as being more representative of the actual energy difference? Explain your answer.

Textbook Question

Using Table 7-2 as a guide, predict which member of each pair is more stable, as well as by about how many kJ/mol or kcal/mol.

a. cis,cis-hexa-2,4-diene or trans,trans-hexa-2,4-diene

b. 2-methylbut-1-ene or 3-methylbut-1-ene

c. 2-methylbut-1-ene or 2-methylbut-2-ene

d. cis-4-methylpent-2-ene or 2-methylpent-2-ene

Textbook Question

Which species in each pair is more stable?

Textbook Question

Conjugated dienes, molecules containing two alkenes separated by one single bond, are discussed in detail in Chapter 21.

(a) Considering the observed ∆H° of hydrogenation, is hexa-1,3-diene (conjugated) or hexa-1,4-diene (unconjugated) more stable?

Textbook Question

Conjugated dienes, molecules containing two alkenes separated by one single bond, are discussed in detail in Chapter 21.

(b) How might you account for this difference in stability?

Textbook Question

Bromination of buta-1,3-diene with a single equivalent of Br₂ can give either of two products. (a) Which of these products (A or B) would you predict to be more stable? Justify your answer.

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Which species in each pair is more stable? f.

Key Concepts

Stability of Chemical Species

Resonance Structures

Electronegativity and Inductive Effects

Watch next

Which species in each pair is more stable?
f.