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

EAS:Friedel-Crafts Alkylation Mechanism

Organic Chemistry

19. Reactions of Aromatics: EAS and Beyond

EAS:Friedel-Crafts Alkylation Mechanism

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Problem 32d

Textbook Question

Predict the product of the following Friedel–Crafts alkylation reactions. Assume only one alkyl group adds in each case.
(d)

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Identify the reactants: The reaction involves benzene and chlorocyclopentane in the presence of aluminum chloride (AlCl₃) as a catalyst.

Understand the mechanism: Friedel-Crafts alkylation involves the formation of a carbocation intermediate. The chlorine atom in chlorocyclopentane will leave, forming a cyclopentyl carbocation.

Consider carbocation stability: The cyclopentyl carbocation is relatively stable and will act as the electrophile in the reaction.

Electrophilic aromatic substitution: The cyclopentyl carbocation will attack the benzene ring, forming a sigma complex (arenium ion) and eventually leading to the substitution of a hydrogen atom on the benzene ring with the cyclopentyl group.

Predict the product: The final product will be cyclopentylbenzene, where the cyclopentyl group is attached to the benzene ring.

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Key Concepts

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

Friedel-Crafts Alkylation

Friedel-Crafts alkylation is a reaction that introduces an alkyl group into an aromatic ring using an alkyl halide and a Lewis acid catalyst, typically aluminum chloride (AlCl3). This electrophilic substitution reaction allows for the formation of new carbon-carbon bonds, enhancing the complexity of aromatic compounds. However, it can lead to polysubstitution and rearrangements, so careful control of conditions is necessary.

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. The aromatic system's electron-rich nature makes it susceptible to attack by electrophiles, leading to the formation of a sigma complex. This mechanism is crucial for understanding how substituents affect the reactivity and orientation of further substitutions on the aromatic ring.

Rearrangement of Carbocations

In Friedel-Crafts reactions, the formation of carbocations is a key step, and these intermediates can undergo rearrangement to form more stable structures. For instance, if a secondary or tertiary carbocation is formed, it may rearrange to a more stable tertiary carbocation before reacting with the aromatic ring. Understanding carbocation stability and rearrangement is essential for predicting the products of alkylation reactions.

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Related Practice

Textbook Question

Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the a position. Predict the major products of the reactions of naphthalene with the following reagents.

(d) isobutylene and HF

Textbook Question

Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the 1-position. Predict the major products of the reactions of naphthalene with the following reagents.

(e) cyclohexanol and BF₃

Textbook Question

For each reaction, show the generation of the electrophile and predict the products.

c. tert-butylbenzene + 2-methylpropene + HF

Textbook Question

For each reaction, show the generation of the electrophile and predict the products.

d. propan-2-ol + toluene + BF₃

Textbook Question

What is the major product of a Friedel–Crafts alkylation using the following alkyl chlorides?

e. (CH₃)₂CHCH₂Cl

f. CH₂=CHCH₂Cl

Textbook Question

Design a synthesis for each of the following, using an intramolecular reaction:

Textbook Question

What product is obtained from the reaction of excess benzene with each of the following reagents?

c. dichloromethane + AlCl₃

Textbook Question

Propose products (if any) and mechanisms for the following AlCl₃-catalyzed reactions:

a. chlorocyclohexane with benzene

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Predict the product of the following Friedel–Crafts alkylation reactions. Assume only one alkyl group adds in each case.(d)

Key Concepts

Friedel-Crafts Alkylation

Electrophilic Aromatic Substitution

Rearrangement of Carbocations

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Predict the product of the following Friedel–Crafts alkylation reactions. Assume only one alkyl group adds in each case.
(d)