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

6. Thermodynamics and Kinetics

Carbocation Stability

Organic Chemistry

6. Thermodynamics and Kinetics

Carbocation Stability

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4:57 minutes

Problem 4a

Textbook Question

Rank the following carbocations in each set from most stable to least stable:
a.

Verified step by step guidance

Step 1: Analyze the stability of carbocations based on their degree of substitution. Tertiary carbocations (attached to three alkyl groups) are more stable than secondary carbocations (attached to two alkyl groups), which are more stable than primary carbocations (attached to one alkyl group).

Step 2: Consider the inductive effect. Alkyl groups donate electron density through sigma bonds, stabilizing the positive charge on the carbocation. More alkyl groups around the carbocation increase stability.

Step 3: Evaluate hyperconjugation. Hyperconjugation occurs when adjacent C-H bonds donate electron density to the carbocation, further stabilizing it. More alkyl groups provide more hyperconjugation opportunities.

Step 4: Examine the structures provided: I is a tertiary carbocation, II is a secondary carbocation, III is a primary carbocation, and IV is a secondary carbocation. Based on substitution, I is the most stable, followed by II and IV (both secondary), and III is the least stable.

Step 5: Rank the carbocations from most stable to least stable: I > II ≈ IV > III. Note that II and IV are similarly stable because they are both secondary carbocations with similar alkyl group environments.

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Key Concepts

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

Carbocation Stability

Carbocations are positively charged carbon species that are classified based on their stability. The stability of a carbocation increases with the number of alkyl groups attached to the positively charged carbon. This is due to hyperconjugation and the inductive effect, where alkyl groups donate electron density, stabilizing the positive charge.

Hyperconjugation

Hyperconjugation is a stabilizing interaction that occurs when the electrons in a sigma bond (C-H or C-C) interact with an adjacent empty p-orbital of a carbocation. This delocalization of electrons helps to spread out the positive charge, thereby increasing the stability of the carbocation. The more hyperconjugative interactions available, the more stable the carbocation.

Inductive Effect

The inductive effect refers to the electron-withdrawing or electron-donating effects transmitted through sigma bonds in a molecule. Alkyl groups are electron-donating, which can help stabilize a carbocation by reducing the positive charge's density. The inductive effect is particularly significant in determining the relative stability of carbocations, with tertiary carbocations being the most stable due to the presence of three electron-donating alkyl groups.

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Rank the following carbocations in each set from most stable to least stable:a.

Key Concepts

Carbocation Stability

Hyperconjugation

Inductive Effect

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Rank the following carbocations in each set from most stable to least stable:
a.