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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5:34 minutes

Problem 28(a)

Textbook Question

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

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Analyze the starting material: trans-but-2-ene is an alkene with a double bond between the second and third carbons, and the substituents on the double bond are on opposite sides (trans configuration).

Identify the reaction type: The transformation involves the formation of a cyclopropane ring, which suggests a cyclopropanation reaction. This typically occurs when an alkene reacts with a carbene or a carbene precursor.

Determine the reagent: A common reagent for cyclopropanation is a carbene generated from a compound like CH2I2 (diiodomethane) in the presence of Zn(Cu) (Simmons-Smith reaction). This reagent adds a CH2 group across the double bond of the alkene.

Predict the stereochemistry: Since the starting alkene is trans, the stereochemistry of the substituents on the cyclopropane ring will also be trans. This is because the reaction is stereospecific, preserving the relative configuration of the substituents on the double bond.

Write the product: The product will be trans-1,2-dimethylcyclopropane, where the two methyl groups are on opposite sides of the cyclopropane ring, reflecting the trans configuration of the starting alkene.

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Key Concepts

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

Elimination Reactions

Elimination reactions involve the removal of atoms or groups from a molecule, resulting in the formation of a double bond or a ring structure. In the context of alkenes, such as trans-but-2-ene, elimination can lead to cyclization, where the molecule forms a cyclic structure. Understanding the mechanism of elimination is crucial for predicting the products of reactions involving alkenes.

Cyclopropane Formation

Cyclopropane formation occurs when a three-membered ring is created from a linear or branched alkene. This reaction typically involves the addition of reagents that facilitate the closure of the ring, often through a concerted mechanism. In the case of trans-but-2-ene, the formation of trans-1,2-dimethylcyclopropane illustrates how stereochemistry plays a role in the final product.

Stereochemistry

Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In reactions involving alkenes and cyclopropanes, the stereochemical configuration (cis or trans) can significantly influence the stability and reactivity of the products. Understanding stereochemistry is essential for predicting the outcomes of reactions and the properties of the resulting compounds.

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Related Practice

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

How many stereoisomers of each product could be obtained?

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

Textbook Question

What are the products of the following reaction?

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