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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6:18 minutes

Problem 86b

Textbook Question

Which species in each pair is more stable?
b.

Verified step by step guidance

Step 1: Analyze the stability of carbocations based on their degree of substitution. Carbocations are classified as primary, secondary, or tertiary depending on the number of alkyl groups attached to the positively charged carbon. More substituted carbocations are generally more stable due to hyperconjugation and inductive effects.

Step 2: Compare the two species in the pair. The first species, CH3C+HCH2CH3, is a secondary carbocation because the positively charged carbon is attached to two alkyl groups (CH3 and CH2CH3). The second species, CH3CH2CH2C+H2, is a primary carbocation because the positively charged carbon is attached to only one alkyl group (CH2CH2CH3).

Step 3: Consider hyperconjugation. Secondary carbocations benefit from more hyperconjugation interactions compared to primary carbocations, as they have more adjacent C-H bonds that can donate electron density to stabilize the positive charge.

Step 4: Evaluate inductive effects. Alkyl groups are electron-donating through inductive effects, which help stabilize the positive charge on the carbocation. Secondary carbocations have more alkyl groups contributing to this stabilization compared to primary carbocations.

Step 5: Conclude that CH3C+HCH2CH3 (secondary carbocation) is more stable than CH3CH2CH2C+H2 (primary carbocation) due to the combined effects of hyperconjugation and inductive stabilization.

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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 degree of substitution: primary, secondary, and tertiary. Tertiary carbocations are the most stable due to hyperconjugation and the inductive effect from surrounding alkyl groups, which help to disperse the positive charge. Understanding the stability of carbocations is crucial for predicting the reactivity and outcomes of organic reactions.

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 or a positively charged carbon. This effect allows for the delocalization of charge, which stabilizes carbocations. The more alkyl groups attached to the positively charged carbon, the greater the hyperconjugation, leading to increased stability.

Inductive Effect

The inductive effect refers to the electron-donating or withdrawing effects of substituents through sigma bonds. Alkyl groups are electron-donating and can stabilize positive charges on carbocations by pushing electron density towards the positively charged carbon. This effect is significant in determining the relative stability of carbocations, as more electron-donating groups lead to greater stability.

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Which species in each pair is more stable? b.

Key Concepts

Carbocation Stability

Hyperconjugation

Inductive Effect

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Which species in each pair is more stable?
b.