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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6:51 minutes

Problem 68b

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?

Verified step by step guidance

Step 1: Understand the reaction. The nitronium ion (NO₂⁺) is an electrophile that reacts with benzene and p-xylene in an electrophilic aromatic substitution reaction. Benzene and p-xylene are the reactants, and the products are nitrobenzene and nitro-p-xylene, respectively.

Step 2: Analyze the reactivity of benzene and p-xylene. Benzene is less reactive toward electrophilic aromatic substitution because it lacks electron-donating groups. In contrast, p-xylene has two methyl groups, which are electron-donating and activate the aromatic ring, making it more reactive toward the nitronium ion.

Step 3: Consider the regioselectivity of the reaction. The methyl groups on p-xylene direct the nitronium ion to the ortho and para positions due to their electron-donating inductive and hyperconjugative effects. This increases the likelihood of nitro-p-xylene formation compared to nitrobenzene.

Step 4: Relate the product distribution to the reactivity. Since p-xylene is more reactive than benzene, it reacts preferentially with the nitronium ion. This explains why a larger amount of nitro-p-xylene (0.098 mol) was formed compared to nitrobenzene (0.002 mol).

Step 5: Conclude the reasoning. The difference in product amounts is due to the higher reactivity of p-xylene, which is activated by its methyl groups, compared to benzene, which lacks activating substituents. This leads to a preferential reaction of the nitronium ion with p-xylene.

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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, the nitronium ion acts as the electrophile, attacking the benzene and p-xylene. The reactivity of the aromatic compounds and the stability of the resulting intermediates influence the distribution of products formed.

Substituent Effects on Reactivity

The presence of substituents on an aromatic ring can significantly affect its reactivity towards electrophiles. In the case of p-xylene, which has two methyl groups, these groups are electron-donating and activate the ring towards further substitution. This results in a higher likelihood of forming one product over the other, depending on the position of substitution and the stability of the intermediates.

Product Distribution and Kinetics

The distribution of products in a reaction can be influenced by both thermodynamic and kinetic factors. In this scenario, the formation of one product over the other may be due to the stability of the transition states or intermediates involved in the reaction. The more stable product is often formed in greater quantities, reflecting the reaction's pathway and the relative energies of the products.

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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.

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

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Which of the following phenoxides should be a stronger nucleophile?

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