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

16. Conjugated Systems

Conjugated Hydrohalogenation (1,2 vs 1,4 addition)

Organic Chemistry

16. Conjugated Systems

Conjugated Hydrohalogenation (1,2 vs 1,4 addition)

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7:18 minutes

Problem 103b

Textbook Question

How many stereoisomers of each product could be obtained?

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Step 1: Analyze the reaction type. The given reaction involves an alkene (cyclohexene) reacting with bromine (Br₂). This is a halogenation reaction where bromine adds across the double bond of the alkene.

Step 2: Determine the product structure. Bromine will add to the double bond in an anti-addition manner, resulting in a vicinal dibromide. The product will have two bromine atoms attached to adjacent carbons that were part of the double bond.

Step 3: Assess stereochemistry. Since bromine adds in an anti manner, the two bromine atoms will be added on opposite faces of the cyclohexane ring. This creates stereoisomers due to the spatial arrangement of the bromine atoms.

Step 4: Count possible stereoisomers. The two carbons where bromine is added become stereogenic centers. Each stereogenic center can have two configurations (R or S), leading to a total of 2ⁿ stereoisomers, where n is the number of stereogenic centers. In this case, n = 2, so there are 2² = 4 possible stereoisomers.

Step 5: Verify the stereoisomers. The four stereoisomers include two pairs of enantiomers (mirror images) due to the anti-addition mechanism. These stereoisomers are distinct and can be represented using wedge and dash bonds in the product structure.

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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 enantiomers, which are non-superimposable mirror images, and diastereomers, which are not mirror images of each other.

Chirality

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. A chiral molecule typically has at least one carbon atom bonded to four different substituents, creating two distinct enantiomers. Understanding chirality is crucial for determining the number of stereoisomers, as each chiral center can lead to multiple configurations.

Counting Stereoisomers

The number of stereoisomers for a compound can be calculated using the formula 2^n, where n is the number of chiral centers in the molecule. This formula accounts for the fact that each chiral center can exist in two configurations (R or S). Additionally, if there are any elements of symmetry in the molecule, they may reduce the total number of unique stereoisomers.

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Related Practice

Textbook Question

Would you expect the following nucleophiles to do 1,2- or 1,4-addition?

(d)

(e)

(f)

Textbook Question

Propose a mechanism for each reaction, showing explicitly how the observed mixtures of products are formed.

c. cyclopenta-1,3-diene + Br₂ → 3,4-dibromocyclopent-1-ene + 3,5-dibromocyclopent-1-ene

Textbook Question

When Br₂ is added to buta-1,3-diene at –15 °C, the product mixture contains 60% of product A and 40% of product B. When the same reaction takes place at 60 °C, the product ratio is 10% A and 90% B.

d. If you had a solution of pure A, and its temperature were raised to 60 °C, what would you expect to happen? Propose a mechanism to support your prediction.

Textbook Question

What are the products of the following reactions, assuming that one equivalent of each reagent is used in each reaction? Disregard stereoisomers.

Textbook Question

What are the products of the following reactions, assuming that one equivalent of each reagent is used in each reaction?

Textbook Question

a. How could each of the following compounds be prepared from a hydrocarbon in a single step?

b. What other organic compound would be obtained from each synthesis?

Textbook Question

a. When HBr adds to a conjugated diene, what is the rate-determining step?

b. When HBr adds to a conjugated diene, what is the product-determining step?

Textbook Question

Draw the major products obtained from the reaction of one equivalent of HCl with the following compounds. For each reaction, indicate the kinetic and thermodynamic products.

a. 2,3-dimethyl-1,3-pentadiene

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