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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6:14 minutes

Problem 25

Textbook Question

Rank the following compounds from most reactive to least reactive in an electrophilic aromatic substitution reaction:

Verified step by step guidance

Step 1: Understand the concept of electrophilic aromatic substitution (EAS). In EAS, the reactivity of a benzene ring depends on the substituents attached to it. Electron-donating groups (EDGs) activate the ring, making it more reactive, while electron-withdrawing groups (EWGs) deactivate the ring, making it less reactive.

Step 2: Analyze the substituents on each compound. (i) has an ethyl group, which is an electron-donating group via hyperconjugation. (ii) has a methoxy group (-OCH3), which is a strong electron-donating group due to resonance and inductive effects. (iii) has a nitro group (-NO2), which is a strong electron-withdrawing group due to resonance and inductive effects. (iv) has an aldehyde group (-CHO), which is an electron-withdrawing group due to inductive effects.

Step 3: Rank the substituents based on their activating or deactivating effects. Methoxy (-OCH3) is the strongest activator, followed by ethyl (-CH2CH3). Aldehyde (-CHO) is a moderate deactivator, and nitro (-NO2) is the strongest deactivator.

Step 4: Predict the reactivity of the compounds in EAS. The compound with the strongest electron-donating group will be the most reactive, while the compound with the strongest electron-withdrawing group will be the least reactive.

Step 5: Rank the compounds from most reactive to least reactive based on the substituents: (ii) > (i) > (iv) > (iii).

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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. The reaction typically involves the formation of a sigma complex, where the aromaticity is temporarily lost, followed by deprotonation to restore aromaticity. Understanding the mechanism and the role of the electrophile is crucial for predicting the reactivity of different aromatic compounds.

Activating and Deactivating Groups

In EAS, substituents on the aromatic ring can either activate or deactivate the ring towards further substitution. Activating groups, such as alkyl groups or electron-donating groups (like -OCH3), increase the electron density of the ring, making it more reactive. Conversely, deactivating groups, such as nitro (-NO2) or carbonyl (-C=O) groups, withdraw electron density, reducing reactivity. The nature of these groups significantly influences the order of reactivity in EAS.

Ortho/Para vs. Meta Directing Effects

Substituents on an aromatic ring can also influence the position where new substituents are added during EAS. Ortho and para directing groups favor substitution at the ortho or para positions relative to themselves, while meta directing groups lead to substitution at the meta position. This directing effect is essential for predicting the products of EAS reactions and understanding the overall reactivity of the compounds in the given question.

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