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

19. Reactions of Aromatics: EAS and Beyond

Electrophilic Aromatic Substitution

Organic Chemistry

19. Reactions of Aromatics: EAS and Beyond

Electrophilic Aromatic Substitution

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2:12 minutes

Problem 55a

Textbook Question

What products would you expect from the following coupling reactions?
(a)

Verified step by step guidance

Step 1: Identify the type of reaction. This is a coupling reaction involving an aryl halide (bromobenzene) and a Gilman reagent (R2CuLi). Gilman reagents are organocuprates that facilitate the formation of carbon-carbon bonds.

Step 2: Recognize the role of the Gilman reagent. The Gilman reagent donates one of its alkyl groups (R group) to replace the halogen atom (Br) on the aryl halide. This substitution results in the formation of a new C-C bond.

Step 3: Analyze the structure of the reactants. The aryl halide is bromobenzene, and the Gilman reagent is [(CH3CH2CH2CH2)CuLi]2. The alkyl group from the Gilman reagent is a butyl group (CH3CH2CH2CH2).

Step 4: Predict the product. The butyl group from the Gilman reagent will replace the bromine atom on the benzene ring, forming butylbenzene (C6H5CH2CH2CH2CH3).

Step 5: Verify the reaction mechanism. The reaction proceeds via oxidative addition of the aryl halide to the copper center, followed by reductive elimination to form the new C-C bond and release the product.

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Key Concepts

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

Coupling Reactions

Coupling reactions are a type of organic reaction where two fragments are joined together, typically involving the formation of a new carbon-carbon bond. These reactions are crucial in organic synthesis for constructing complex molecules. Common examples include the Suzuki and Sonogashira reactions, which utilize palladium or copper catalysts to facilitate the coupling of aryl or vinyl halides with nucleophiles.

Organocuprates

Organocuprates, such as the reagent shown in the question (R2CuLi), are organometallic compounds that contain a carbon atom bonded to a copper atom. They are highly nucleophilic and are often used in coupling reactions to react with electrophiles, such as alkyl or aryl halides. Their ability to form stable carbon-carbon bonds makes them valuable in synthetic organic chemistry.

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. In the context of the question, the bromobenzene acts as an electrophile, and the organocuprate can facilitate the substitution process, leading to the formation of a new carbon-carbon bond on the aromatic system. Understanding EAS is essential for predicting the products of reactions involving aromatic compounds.

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Related Practice

Textbook Question

Furan undergoes electrophilic aromatic substitution more readily than benzene; mild reagents and conditions are sufficient. For example, furan reacts with bromine to give 2-bromofuran.

b. Explain why furan undergoes bromination (and other electrophilic aromatic substitutions) primarily at the 2-position.

Textbook Question

Furan undergoes electrophilic aromatic substitution more readily than benzene; mild reagents and conditions are sufficient. For example, furan reacts with bromine to give 2-bromofuran.

a. Propose mechanisms for the bromination of furan at the 2-position and at the 3-position. Draw the resonance forms of each sigma complex, and compare their stabilities.

Textbook Question

Styrene (vinylbenzene) undergoes electrophilic aromatic substitution much faster than benzene, and the products are found to be primarily ortho- and para-substituted styrenes. Use resonance forms of the intermediates to explain these results.

Textbook Question

What products would you expect from the following coupling reactions?

(b)

Textbook Question

Show how each of the following compounds can be prepared from methyl phenyl ketone:

Textbook Question

Indicate how the following compounds can be synthesized from cyclohexanone and any other necessary reagents:

Textbook Question

Pyrrole undergoes electrophilic aromatic substitution more readily than benzene, and mild reagents and conditions are sufficient. These reactions normally occur at the 2-position rather than the 3-position, as shown in the following example.

b. Explain why pyrrole reacts more readily than benzene, and also why substitution occurs primarily at the 2-position rather than the 3-position.

Textbook Question

a. Draw resonance contributors to show why pyridine-N-oxide is more reactive than pyridine toward electrophilic aromatic substitution.

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