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

Electron Withdrawing Groups

Organic Chemistry

19. Reactions of Aromatics: EAS and Beyond

Electron Withdrawing Groups

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5:58 minutes

Problem 60

Textbook Question

Why is anisole nitrated more rapidly than thioanisole under the same conditions?

Verified step by step guidance

Understand the structures of anisole and thioanisole: Anisole is an aromatic compound with a methoxy group (-OCH₃) attached to the benzene ring, while thioanisole has a thiomethyl group (-SCH₃) attached to the benzene ring.

Analyze the electron-donating or withdrawing effects of the substituents: The methoxy group (-OCH₃) in anisole is an electron-donating group due to the lone pairs on the oxygen atom, which can participate in resonance with the benzene ring. In contrast, the thiomethyl group (-SCH₃) in thioanisole is less effective at donating electrons because sulfur is less electronegative and less efficient at resonance donation compared to oxygen.

Consider the activation of the benzene ring: The electron-donating effect of the methoxy group in anisole increases the electron density on the benzene ring, particularly at the ortho and para positions, making it more reactive toward electrophilic aromatic substitution reactions like nitration. The thiomethyl group in thioanisole also donates electrons but to a lesser extent, resulting in a less activated benzene ring.

Relate this to the nitration reaction: Nitration involves the generation of the nitronium ion (NO₂⁺), a strong electrophile, which reacts with the electron-rich benzene ring. Since anisole has a higher electron density due to the stronger electron-donating effect of the methoxy group, it undergoes nitration more rapidly than thioanisole under the same conditions.

Conclude the comparison: The difference in reactivity is primarily due to the difference in the electron-donating abilities of the substituents (-OCH₃ vs. -SCH₃). The methoxy group in anisole activates the benzene ring more effectively than the thiomethyl group in thioanisole, leading to faster nitration of anisole.

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Key Concepts

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

Nitration Mechanism

Nitration is an electrophilic aromatic substitution reaction where a nitro group is introduced into an aromatic compound. The reaction involves the generation of a nitronium ion (NO2+) that acts as the electrophile. The rate of nitration depends on the electron density of the aromatic ring, which is influenced by substituents attached to it.

Electron Donating and Withdrawing Groups

Substituents on an aromatic ring can either donate or withdraw electron density. Electron-donating groups, like the methoxy group in anisole, increase the electron density of the ring, making it more reactive towards electrophiles. In contrast, thioanisole has a sulfur atom that, while also donating electrons, does so less effectively than the methoxy group, leading to slower nitration.

Resonance Effects

Resonance effects describe how the distribution of electrons in a molecule can stabilize or destabilize certain structures. In anisole, the methoxy group can delocalize electron density into the aromatic ring through resonance, enhancing its reactivity. Thioanisole's sulfur atom does not stabilize the positive charge in the intermediate as effectively, resulting in a slower reaction rate compared to anisole.

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Related Practice

Textbook Question

Rank each group of compounds from most reactive to least reactive toward electrophilic aromatic substitution:

e. p-methylnitrobenzene, 2-chloro-1-methyl-4-nitrobenzene, 1-methyl-2,4-dinitrobenzene, p-chloromethylbenzene

Textbook Question

Rank each group of compounds from most reactive to least reactive toward electrophilic aromatic substitution:

f. bromobenzene, chlorobenzene, fluorobenzene, iodobenzene

Textbook Question

For each horizontal row of substituted benzenes, indicateb. the one that is the least reactive in an electrophilic aromatic substitution reaction.

Textbook Question

For each horizontal row of substituted benzenes, indicate

c. the one that yields the highest percentage of meta product in an electrophilic aromatic substitution reaction.

Textbook Question

A mixture of 0.10 mol benzene and 0.10 mol p-xylene was allowed to react with 0.10 mol nitronium ion until all the nitronium ion was gone. Two products were obtained: 0.002 mol of one and 0.098 mol of the other.

b. Why was more of one product obtained than of the other?

Textbook Question

Indigo is a dye that was originally isolated from coal tar. In 1905, Johann Friedrich Wilhelm Adolf von Baeyer won a Nobel Prize for a method that allowed indigo to be isolated from plants [a green chemist ahead of his time.] If you nitrated indigo using the reaction learned in this chapter, at which carbon would you expect the nitro group to attach?

Textbook Question

Substitution at the benzylic position of the molecules shown was observed to occur at different rates. Explain this observation.

Textbook Question

Which of the following phenoxides should be a stronger nucleophile?

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