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

Halogenation

Organic Chemistry

10. Addition Reactions

Halogenation

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Problem 8

Textbook Question

In which of the two steps in the alkene halogenation mechanism does a redox reaction occur?

Verified step by step guidance

Step 1: Begin by understanding the alkene halogenation mechanism. This reaction involves two main steps: (1) the formation of a halonium ion intermediate and (2) the nucleophilic attack by the halide ion.

Step 2: Recall the definition of a redox reaction. A redox reaction involves the transfer of electrons, where one species is oxidized (loses electrons) and another is reduced (gains electrons).

Step 3: Analyze the first step of the mechanism. When the halogen molecule (e.g., Br₂ or Cl₂) approaches the alkene, the π-electrons of the alkene attack the halogen, forming a halonium ion. In this step, the halogen molecule is reduced as it gains electrons, and the alkene is oxidized as it loses electrons. This is a redox reaction.

Step 4: Examine the second step of the mechanism. The halide ion (e.g., Br⁻ or Cl⁻) attacks the halonium ion to open the ring and form the final dihalogenated product. This step does not involve a transfer of electrons in the sense of oxidation or reduction, so it is not a redox reaction.

Step 5: Conclude that the redox reaction occurs in the first step of the alkene halogenation mechanism, where the halogen molecule is reduced and the alkene is oxidized.

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Key Concepts

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

Alkene Halogenation Mechanism

The alkene halogenation mechanism involves the addition of halogens (like Cl2 or Br2) to an alkene, resulting in a vicinal dihalide. This process typically occurs in two main steps: the formation of a cyclic halonium ion and the subsequent nucleophilic attack by a halide ion. Understanding this mechanism is crucial for identifying where redox reactions may take place.

Redox Reactions

Redox reactions involve the transfer of electrons between species, resulting in changes in oxidation states. In the context of alkene halogenation, the halogen molecule is reduced as it forms a halonium ion, while the alkene is oxidized. Recognizing these electron transfer processes is essential for pinpointing the steps in which redox reactions occur.

Oxidation States

Oxidation states are a way to keep track of electron transfer in chemical reactions. In the alkene halogenation mechanism, the oxidation state of the carbon atoms in the alkene changes as they bond with halogen atoms. Understanding how to assign and interpret oxidation states helps in identifying the specific steps where redox reactions happen.

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Related Practice

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (i) Br₂

(k)

Textbook Question

Predict the product(s) that would result when the alkenes are allowed to react under the following conditions: (ii) Cl₂

(k)

Textbook Question

Predict the product(s) of each of the following reactions, making sure to indicate the relative stereochemical outcome. Indicate any racemic mixtures by drawing both enantiomers.

(b)

Textbook Question

Predict the product(s) of each of the following reactions, making sure to indicate the relative stereochemical outcome. Indicate any racemic mixtures by drawing both enantiomers.

(f)

Textbook Question

Bromination of a highly electron-rich alkene such as 2-methoxybut-2-ene has been shown to produce approximately equal mixtures of the trans- and cis-dibromide. Suggest an explanation for this observation.

Textbook Question

In Chapter 19, we discuss the reaction of enols with bromine. This reaction produces α -bromoketones in good yields. Suggest a mechanism for this reaction and justify its deviation from the dibromide product you might have expected.

Textbook Question

Identify A through O:

Textbook Question

Predict the product of the following addition reactions to dienes.

(c)

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