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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0:59 minutes

Problem 3b

Textbook Question

Which of the carbocations in part a is most stable?
1. the isobutyl cation?
2. the n-butyl cation?
3. the sec-butyl cation?

Verified step by step guidance

Step 1: Understand the concept of carbocation stability. Carbocation stability is influenced by factors such as the number of alkyl groups attached to the positively charged carbon (hyperconjugation) and the inductive effect. Tertiary carbocations are generally more stable than secondary, which are more stable than primary carbocations.

Step 2: Analyze the structure of the isobutyl cation. The isobutyl cation has a primary carbocation, meaning the positively charged carbon is attached to only one alkyl group. This makes it less stable compared to secondary or tertiary carbocations.

Step 3: Analyze the structure of the n-butyl cation. The n-butyl cation also has a primary carbocation, with the positively charged carbon attached to one alkyl group. Its stability is similar to the isobutyl cation.

Step 4: Analyze the structure of the sec-butyl cation. The sec-butyl cation has a secondary carbocation, where the positively charged carbon is attached to two alkyl groups. This increases its stability due to hyperconjugation and inductive effects.

Step 5: Compare the stability of the three carbocations. Based on the analysis, the sec-butyl cation is the most stable because it is a secondary carbocation, while the isobutyl and n-butyl cations are primary carbocations and therefore less stable.

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Key Concepts

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

Carbocation Stability

Carbocation stability is influenced by the degree of substitution on the positively charged carbon atom. Tertiary carbocations, which have three alkyl groups attached, are more stable than secondary and primary carbocations due to hyperconjugation and inductive effects. The more alkyl groups surrounding the carbocation, the greater the electron-donating effect, which helps to stabilize the positive charge.

Hyperconjugation

Hyperconjugation is a stabilizing interaction that occurs when the electrons in a sigma bond (usually 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 becomes.

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 through the inductive effect. The presence of more alkyl groups around a carbocation enhances its stability due to this electron-donating property.

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Master Determining Carbocation Stability with a bite sized video explanation from Johnny

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Which of the carbocations in part a is most stable?1. the isobutyl cation? 2. the n-butyl cation? 3. the sec-butyl cation?

Key Concepts

Carbocation Stability

Hyperconjugation

Inductive Effect

Watch next

Which of the carbocations in part a is most stable?
1. the isobutyl cation?
2. the n-butyl cation?
3. the sec-butyl cation?