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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2:16 minutes

Problem 2

Textbook Question

Draw resonance structures to identify which of the following is the more stable carbocation.

Verified step by step guidance

Step 1: Understand the concept of resonance. Resonance structures are alternative Lewis structures for a molecule or ion that differ only in the placement of electrons, not the arrangement of atoms. Resonance helps to delocalize charge, increasing stability.

Step 2: Identify the carbocations in the problem. A carbocation is a positively charged carbon atom with only three bonds, leaving it electron-deficient. Stability of carbocations is influenced by resonance and hyperconjugation.

Step 3: Draw the resonance structures for each carbocation. Begin by moving electrons (such as π electrons or lone pairs) to adjacent atoms to create alternative structures. Ensure that the positive charge is delocalized across the molecule in each resonance structure.

Step 4: Evaluate the resonance structures. The more resonance structures a carbocation has, and the more delocalized the positive charge is, the more stable the carbocation. Additionally, check if the resonance structures place the positive charge on more electronegative atoms or in aromatic systems, which further increases stability.

Step 5: Compare the stability of the two carbocations based on their resonance structures. The carbocation with more resonance structures and better charge delocalization will be the more stable one.

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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 can vary in stability based on their structure. Stability increases with the degree of substitution; tertiary carbocations are more stable than secondary, which are more stable than primary. This is due to hyperconjugation and the inductive effect from surrounding alkyl groups that help to disperse the positive charge.

Resonance Structures

Resonance structures are different ways of drawing the same molecule that illustrate the delocalization of electrons. In the context of carbocations, resonance can stabilize the positive charge by allowing it to be shared across multiple atoms. The more resonance structures a carbocation has, the more stable it is, as the charge is less localized.

Electrophilic Stability

Electrophilic stability refers to the ability of a carbocation to stabilize its positive charge through various mechanisms, including resonance and inductive effects. A more stable carbocation will be less reactive and more favorable in chemical reactions. Understanding the factors that contribute to electrophilic stability is crucial for predicting the behavior of carbocations in organic reactions.

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