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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4:14 minutes

Problem 55f

Textbook Question

Rank each group of compounds from most reactive to least reactive toward electrophilic aromatic substitution:
f. bromobenzene, chlorobenzene, fluorobenzene, iodobenzene

Verified step by step guidance

Understand the concept of electrophilic aromatic substitution (EAS): This reaction involves the substitution of a hydrogen atom on an aromatic ring with an electrophile. The reactivity of the aromatic ring depends on the electronic effects of substituents already present on the ring.

Analyze the substituents on the benzene ring: In this case, the substituents are halogens (bromine, chlorine, fluorine, and iodine). Halogens are electron-withdrawing groups due to their inductive effect (-I effect) but also have a resonance-donating effect (+R effect) because of their lone pairs.

Determine the net effect of halogens on reactivity: The inductive effect (-I) of halogens deactivates the ring by withdrawing electron density, making it less reactive toward EAS. However, the resonance effect (+R) can donate electron density back to the ring, partially counteracting the deactivation. The balance between these effects depends on the halogen's electronegativity and size.

Rank the halogens based on their electronegativity and resonance effects: Fluorine is the most electronegative, so its inductive effect dominates, making fluorobenzene the least reactive. Iodine is the least electronegative and has a weaker inductive effect, so its resonance effect is more significant, making iodobenzene the most reactive. Bromine and chlorine fall in between, with bromine being slightly less deactivating than chlorine due to its lower electronegativity.

Conclude the ranking: Based on the analysis, the order of reactivity toward electrophilic aromatic substitution is iodobenzene > bromobenzene > chlorobenzene > fluorobenzene.

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Key Concepts

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

Electrophilic Aromatic Substitution (EAS)

Electrophilic Aromatic Substitution is a fundamental reaction in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. This process is crucial for understanding the reactivity of aromatic compounds, as the stability of the aromatic system influences how readily it can react with electrophiles.

Halogen Substituents and Their Effects

Halogen substituents (like bromine, chlorine, fluorine, and iodine) on an aromatic ring can either activate or deactivate the ring toward electrophilic substitution. While they are generally deactivating due to their electronegativity, their relative positions in the periodic table affect their reactivity, with larger halogens typically being less electronegative and more polarizable, thus influencing the overall reactivity.

Resonance and Inductive Effects

The resonance and inductive effects of substituents on an aromatic ring play a significant role in determining reactivity. Electron-withdrawing groups decrease electron density on the ring, making it less reactive, while electron-donating groups increase electron density, enhancing reactivity. Understanding these effects is essential for ranking the reactivity of halogenated aromatic compounds.

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Related Practice

Textbook Question

List the compounds in each set from most reactive to least reactive toward electrophilic aromatic substitution:

b. dichloromethylbenzene, difluoromethylbenzene, toluene, chloromethylbenzene

Textbook Question

List the compounds in each set from most reactive to least reactive toward electrophilic aromatic substitution:

a. benzene, phenol, toluene, nitrobenzene, bromobenzene

Textbook Question

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

b. 1-chloro-2,4-dinitrobenzene, 2,4-dinitrophenol, 1-methyl-2,4-dinitrobenzene

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

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

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

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?

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Rank each group of compounds from most reactive to least reactive toward electrophilic aromatic substitution:f. bromobenzene, chlorobenzene, fluorobenzene, iodobenzene

Key Concepts

Electrophilic Aromatic Substitution (EAS)

Halogen Substituents and Their Effects

Resonance and Inductive Effects

Watch next

Rank each group of compounds from most reactive to least reactive toward electrophilic aromatic substitution:
f. bromobenzene, chlorobenzene, fluorobenzene, iodobenzene