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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3:40 minutes

Problem 18a,b,c

Textbook Question

Are the following substituents ortho–para directors or meta directors?
a. CH=CHC≡N
b. NO₂
c. CH₂OH

Verified step by step guidance

Step 1: Understand the concept of ortho–para directors and meta directors. Substituents on an aromatic ring influence the position of incoming substituents during electrophilic aromatic substitution. Ortho–para directors are typically electron-donating groups, while meta directors are electron-withdrawing groups.

Step 2: Analyze substituent (a) CH=CHC≡N. This group contains a conjugated system with a nitrile (-C≡N) group, which is strongly electron-withdrawing due to its electronegativity and ability to pull electron density away from the aromatic ring. Electron-withdrawing groups are meta directors.

Step 3: Analyze substituent (b) NO2. The nitro group (-NO2) is a classic example of a strongly electron-withdrawing group due to resonance and inductive effects. It pulls electron density away from the aromatic ring, making it a meta director.

Step 4: Analyze substituent (c) CH2OH. The hydroxymethyl group (-CH2OH) contains an -OH group, which is capable of donating electron density to the aromatic ring through resonance. Electron-donating groups are ortho–para directors.

Step 5: Summarize the findings: Substituent (a) CH=CHC≡N is a meta director, substituent (b) NO2 is a meta director, and substituent (c) CH2OH is an ortho–para director.

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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. Understanding EAS is crucial for determining how different substituents influence the reactivity and orientation of further substitutions on the aromatic compound.

Ortho-Para vs. Meta Directors

Substituents on an aromatic ring can be classified as ortho-para directors or meta directors based on their electronic effects. Ortho-para directors, such as electron-donating groups, stabilize the carbocation intermediate at the ortho and para positions, while meta directors, typically electron-withdrawing groups, destabilize these positions and favor substitution at the meta position.

Resonance and Inductive Effects

Resonance and inductive effects are key concepts that explain how substituents influence the electron density of an aromatic ring. Resonance involves the delocalization of electrons, which can stabilize or destabilize intermediates during reactions, while inductive effects refer to the electron-withdrawing or donating nature of substituents, affecting the overall reactivity and directing effects in electrophilic aromatic substitution.

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Related Practice

Textbook Question

b. Rank the same compounds from greatest tendency to least tendency to undergo electrophilic aromatic substitution.

chlorobenzene, 1-chloro-2,4-dinitrobenzene, p-chloronitrobenzene

Textbook Question

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

a. benzene, ethylbenzene, chlorobenzene, nitrobenzene, anisole

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

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.

Open Question

Draw the resonance contributors for:

a. benzaldehyde

Textbook Question

Despite the amino group being an ortho/para director, nitration of aniline gives the meta isomer predominantly. Explain this result.

Textbook Question

Predict the major product(s) that would result when molecules (a)–(i) are allowed to react under the following conditions. (iv) chlorocyclopentane, AlCl₃, (v) 1-chloro-1-methylcyclohexane , AlCl₃, (vi) PhCOCl, AlCl₃. If no reaction will occur, indicate by writing NR.

(a)

Textbook Question

Predict the products of the following electrophilic aromatic substitution reactions.

(b)

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