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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1:59 minutes

Problem 45c,d

Textbook Question

What stereoisomers are obtained from the following reactions?
c. (E)-3-methyl-2-pentene + HBr
d. cis-3-hexene + HBr

Verified step by step guidance

Step 1: Understand the reaction mechanism. Both reactions involve the addition of HBr to an alkene. This is an electrophilic addition reaction where the π bond of the alkene attacks the proton (H⁺) from HBr, forming a carbocation intermediate.

Step 2: Analyze the structure of the starting alkene. For part (c), (E)-3-methyl-2-pentene is an alkene with the substituents on opposite sides of the double bond. For part (d), cis-3-hexene has substituents on the same side of the double bond.

Step 3: Determine the regioselectivity of the reaction. According to Markovnikov's rule, the bromine (Br⁻) will add to the more substituted carbon of the double bond, as this stabilizes the carbocation intermediate.

Step 4: Consider stereochemistry. The addition of HBr can lead to the formation of stereoisomers due to the planar nature of the carbocation intermediate. The Br⁻ can attack from either side of the carbocation, resulting in a mixture of enantiomers or diastereomers depending on the starting alkene.

Step 5: Predict the stereoisomers formed. For (E)-3-methyl-2-pentene, the addition of HBr will yield two stereoisomers (enantiomers) due to the formation of a chiral center. For cis-3-hexene, the addition of HBr will also yield two stereoisomers (enantiomers) for the same reason. The exact stereoisomers depend on the spatial arrangement of the substituents after the addition.

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Key Concepts

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

Stereoisomerism

Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of those atoms. This can lead to different physical and chemical properties. The two main types of stereoisomers are geometric isomers (cis/trans) and optical isomers (enantiomers). Understanding stereoisomerism is crucial for predicting the outcomes of reactions involving alkenes.

Electrophilic Addition Reactions

Electrophilic addition reactions are a fundamental type of reaction for alkenes, where an electrophile reacts with a nucleophile, typically the double bond of the alkene. In the case of alkenes reacting with HBr, the double bond opens up, allowing the bromine and hydrogen to add across the former double bond. The regioselectivity and stereochemistry of the addition depend on the structure of the alkene and the mechanism of the reaction.

Markovnikov's Rule

Markovnikov's Rule states that in the addition of HX (where X is a halogen) to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This rule helps predict the major product of the reaction, especially in cases where the alkene is asymmetrical. Understanding this rule is essential for determining the stereoisomers formed during the reaction of alkenes with HBr.

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