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 Acylation Mechanism

Organic Chemistry

19. Reactions of Aromatics: EAS and Beyond

EAS:Friedel-Crafts Acylation Mechanism

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3:24 minutes

Problem 53e

Textbook Question

Predict the major products of the following reactions.
(e) p-methylanisole + acetyl chloride + AlCl₃

Verified step by step guidance

Identify the type of reaction: This is a Friedel-Crafts acylation reaction, where an aromatic compound reacts with an acyl chloride in the presence of a Lewis acid catalyst (AlCl₃). The reaction introduces an acyl group (-COCH₃) onto the aromatic ring.

Analyze the structure of p-methylanisole: p-Methylanisole has two substituents on a benzene ring: a methoxy group (-OCH₃) and a methyl group (-CH₃) in the para position relative to each other. Both groups are electron-donating and activate the ring towards electrophilic substitution, directing incoming groups to the ortho and para positions relative to themselves.

Determine the most reactive positions: The methoxy group is a stronger electron-donating group than the methyl group, so it will dominate the directing effects. The ortho and para positions relative to the methoxy group are the most reactive. However, the para position relative to the methoxy group is already occupied by the methyl group, so the acyl group will primarily add to the ortho positions relative to the methoxy group.

Generate the intermediate: The acetyl chloride (CH₃COCl) reacts with AlCl₃ to form the acylium ion (CH₃C⁺=O), which is the electrophile in this reaction. This electrophile will attack the most reactive positions on the aromatic ring, leading to the formation of a sigma complex (arenium ion).

Complete the reaction: The sigma complex will lose a proton to regenerate the aromaticity of the ring, resulting in the major product. The major product will be p-methylanisole with an acetyl group (-COCH₃) added to the ortho position relative to the methoxy group.

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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. In this case, p-methylanisole, which has a methoxy group that activates the ring, will undergo substitution with acetyl chloride in the presence of a Lewis acid catalyst like AlCl3, facilitating the reaction.

Activating and Deactivating Groups

In EAS reactions, substituents on the aromatic ring can either activate or deactivate the ring towards further substitution. The methoxy group in p-methylanisole is an activating group, which enhances the electron density of the ring, making it more reactive towards electrophiles like acetyl chloride, while the methyl group also directs substitution to the para position.

Regioselectivity

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others. In the case of p-methylanisole reacting with acetyl chloride, the presence of the activating groups will lead to the major product being the para-substituted acetophenone derivative, as the methoxy and methyl groups direct the electrophile to the para position relative to themselves.

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