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

7. Substitution Reactions

Good Leaving Groups

Organic Chemistry

7. Substitution Reactions

Good Leaving Groups

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1:12 minutes

Problem 24b

Textbook Question

Formation of the carbocation should be fastest for which leaving group?
(b)

Verified step by step guidance

Identify the factors that influence the rate of carbocation formation. Carbocation formation is typically influenced by the stability of the carbocation intermediate and the ability of the leaving group to depart. A good leaving group is one that can stabilize the negative charge after leaving.

Examine the leaving groups in the given options. A good leaving group is usually a weak base, as weak bases are more stable on their own. For example, halides like Cl⁻, Br⁻, and I⁻ are common leaving groups, with I⁻ being the best due to its larger size and better charge distribution.

Consider the stability of the carbocation intermediate. Carbocations are stabilized by factors such as resonance, hyperconjugation, and inductive effects. A more stable carbocation will form more readily.

Compare the leaving groups in the given options to determine which one is the best leaving group. The leaving group that is the weakest base (most stable after leaving) will facilitate the fastest carbocation formation.

Combine the analysis of the leaving group and carbocation stability to determine the overall rate of carbocation formation for each option. The option with the best leaving group and the most stable carbocation will have the fastest rate of carbocation formation.

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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 be stabilized by adjacent alkyl groups through hyperconjugation and inductive effects. The more stable the carbocation, the faster it can form. Tertiary carbocations are more stable than secondary, which are more stable than primary, due to the number of alkyl groups that can donate electron density to the positively charged carbon.

Leaving Group Ability

The ability of a leaving group to depart from a molecule is crucial in determining the rate of a reaction. Good leaving groups are typically weak bases that can stabilize the negative charge after leaving. Common examples include halides like iodide and bromide, which are better leaving groups than fluoride or hydroxide due to their ability to stabilize the negative charge.

Reaction Mechanisms

Understanding the mechanism of a reaction is essential for predicting the formation of intermediates like carbocations. In nucleophilic substitution reactions, the leaving group departs, allowing the nucleophile to attack the carbocation. The rate of this process can be influenced by the nature of the leaving group and the stability of the resulting carbocation, which ultimately determines the speed of the reaction.

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