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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4:10 minutes

Problem 50a,b

Textbook Question

Predict the major products formed when benzene reacts (just once) with the following reagents.
a. tert-butyl bromide, AlCl₃
b. 1-chlorobutane, AlCl₃

Verified step by step guidance

Step 1: Recognize that the reaction involves benzene and an alkyl halide in the presence of AlCl₃, which is a Friedel-Crafts alkylation reaction. This reaction introduces an alkyl group onto the benzene ring.

Step 2: For part (a), tert-butyl bromide (C(CH₃)₃Br) reacts with AlCl₃ to form a tert-butyl carbocation (C(CH₃)₃⁺) as the electrophile. This occurs because AlCl₃ acts as a Lewis acid, abstracting the bromide ion (Br⁻) from tert-butyl bromide.

Step 3: The tert-butyl carbocation then reacts with the benzene ring via electrophilic aromatic substitution. The π-electrons of the benzene ring attack the carbocation, forming a sigma complex (arenium ion). This intermediate is stabilized by resonance.

Step 4: The sigma complex loses a proton (H⁺) to restore aromaticity, resulting in the formation of tert-butylbenzene as the major product.

Step 5: For part (b), 1-chlorobutane (CH₃CH₂CH₂CH₂Cl) reacts with AlCl₃ to form a primary butyl carbocation (CH₃CH₂CH₂CH₂⁺). However, primary carbocations are unstable and undergo hydride shifts to form a more stable secondary carbocation (CH₃CH₂CH⁺CH₃). This secondary carbocation then reacts with benzene in the same manner as described in steps 3 and 4, leading to the formation of sec-butylbenzene as the major product.

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Key Concepts

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

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This process is crucial for understanding how benzene and its derivatives react with various reagents, as it preserves the aromaticity of the ring while introducing new substituents.

Friedel-Crafts Alkylation

Friedel-Crafts alkylation is a specific type of electrophilic aromatic substitution that involves the introduction of an alkyl group onto an aromatic ring using an alkyl halide and a Lewis acid catalyst, such as AlCl3. This reaction can lead to the formation of branched or linear alkyl groups, depending on the structure of the alkyl halide used.

Rearrangement of Carbocations

The stability and rearrangement of carbocations play a critical role in reactions involving alkyl halides. When an alkyl halide reacts in a Friedel-Crafts alkylation, the formation of a carbocation intermediate can lead to rearrangements, resulting in more stable carbocations, which can affect the final product distribution.

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Related Practice

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

Textbook Question

Predict the products.

Textbook Question

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

b. methyl chloride with anisole

Textbook Question

Predict the major products formed when benzene reacts (just once) with the following reagents.

c. isobutyl alcohol + BF₃

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

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