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

11. Radical Reactions

Anti Markovnikov Addition of Br

Organic Chemistry

11. Radical Reactions

Anti Markovnikov Addition of Br

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Problem 38b

Textbook Question

Draw the structures of four six-carbon alkenes that form the same product, whether they react with HBr in the presence of a peroxide or with HBr in the absence of a peroxide.

Verified step by step guidance

Identify the key concept: The problem involves the addition of HBr to alkenes. In the presence of a peroxide, the reaction follows the anti-Markovnikov rule (radical mechanism), while in the absence of a peroxide, it follows the Markovnikov rule (ionic mechanism). The goal is to find alkenes that yield the same product regardless of the mechanism.

Understand the structural requirement: For the product to be the same in both cases, the alkene must be symmetrical or structured such that the addition of HBr (whether Markovnikov or anti-Markovnikov) leads to the same product. This typically happens when the two carbons of the double bond are equally substituted or when the product is identical due to symmetry.

Draw the first structure: Consider a symmetrical alkene, such as 3-hexene. The double bond is in the middle of the chain, and both sides are identical. Adding HBr in either mechanism will yield the same product.

Draw the second structure: Consider a terminal alkene, such as 1-hexene. In this case, the addition of HBr will always result in the same product because the anti-Markovnikov and Markovnikov products are indistinguishable for this structure.

Draw additional structures: Explore other symmetrical or unique alkenes, such as 2,3-dimethyl-2-butene (a symmetrical alkene) or 2-hexene (cis or trans). These structures also satisfy the condition of forming the same product regardless of the reaction mechanism.

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Key Concepts

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

Alkenes and Their Structures

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond (C=C). The presence of this double bond allows for geometric isomerism and influences the reactivity of the molecule. Understanding the structural representation of alkenes is crucial for predicting their behavior in chemical reactions, particularly in electrophilic additions.

Electrophilic Addition Reactions

Electrophilic addition is a fundamental reaction mechanism in organic chemistry where an electrophile reacts with a nucleophile, typically involving alkenes. In the case of HBr addition, the reaction can proceed via different pathways depending on the presence of peroxides, which can lead to anti-Markovnikov addition. Recognizing how these mechanisms differ is essential for predicting the products formed from the alkenes.

Peroxide Effect (Anti-Markovnikov Addition)

The peroxide effect refers to the phenomenon where the addition of HBr to alkenes in the presence of peroxides leads to the formation of products that follow anti-Markovnikov's rule. This means that the bromine atom attaches to the less substituted carbon atom of the double bond. Understanding this effect is key to determining the structures of the alkenes that yield the same product under both reaction conditions.

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