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

10. Addition Reactions

Hydrohalogenation

Organic Chemistry

10. Addition Reactions

Hydrohalogenation

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2:56 minutes

Problem 2b

Textbook Question

When 1-chlorocyclohexene reacts with HBr, the major product is 1-bromo-1-chlorocyclohexane. Propose a mechanism for this reaction, and explain why your proposed intermediate is more stable than the other possible intermediate

Verified step by step guidance

Step 1: Begin by identifying the reactants and the type of reaction. The reactants are 1-chlorocyclohexene and HBr, and the reaction involves electrophilic addition of HBr to the double bond in the cyclohexene ring.

Step 2: The first step in the mechanism is protonation of the double bond. The π-electrons of the double bond attack the hydrogen atom of HBr, forming a carbocation intermediate. Use MathML to represent the protonation step: `

{CH}_{2} (CH) = CH (CH)

Step 3: Consider the stability of the carbocation intermediate. The protonation can lead to two possible carbocations: a secondary carbocation at the 2-position or a tertiary carbocation at the 1-position. The tertiary carbocation is more stable due to hyperconjugation and inductive effects from the adjacent chlorine atom, which stabilizes the positive charge.

Step 4: The bromide ion (Br⁻) generated in the first step now acts as a nucleophile and attacks the more stable tertiary carbocation. This results in the formation of the major product, 1-bromo-1-chlorocyclohexane.

Step 5: Summarize why the tertiary carbocation intermediate is favored. The chlorine atom at the 1-position exerts an inductive electron-withdrawing effect, stabilizing the positive charge on the carbocation. Additionally, tertiary carbocations are inherently more stable than secondary carbocations due to hyperconjugation and the distribution of charge.

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Key Concepts

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

Electrophilic Addition Mechanism

The reaction of 1-chlorocyclohexene with HBr follows an electrophilic addition mechanism, where the double bond acts as a nucleophile, attacking the electrophilic hydrogen in HBr. This results in the formation of a carbocation intermediate. Understanding this mechanism is crucial as it sets the stage for the subsequent steps leading to the final product.

Carbocation Stability

Carbocation stability is a key factor in determining the major product of electrophilic addition reactions. Carbocations can be classified as primary, secondary, or tertiary based on the number of alkyl groups attached to the positively charged carbon. Tertiary carbocations are the most stable due to hyperconjugation and inductive effects, which help to stabilize the positive charge.

Regioselectivity

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others. In the case of the reaction between 1-chlorocyclohexene and HBr, the formation of 1-bromo-1-chlorocyclohexane is favored due to the stability of the carbocation intermediate formed during the reaction. This concept is essential for predicting the major product in electrophilic addition reactions.

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