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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8:25 minutes

Problem 82

Textbook Question

Using resonance contributors for the carbocation intermediate, explain why a phenyl group is an ortho–para director.

Verified step by step guidance

Identify the key concept: A phenyl group is an aromatic ring, and its ability to direct substituents to the ortho and para positions is due to resonance stabilization of the carbocation intermediate formed during electrophilic aromatic substitution.

Draw the resonance structures of the phenyl group with a substituent at the ortho position. Show how the delocalization of the positive charge through the aromatic ring stabilizes the carbocation intermediate. Use curved arrows to indicate electron movement.

Repeat the process for the para position. Draw the resonance structures and demonstrate how the positive charge is delocalized across the aromatic ring, providing similar stabilization as in the ortho position.

Compare the resonance structures for the ortho and para positions to those for the meta position. For the meta position, the positive charge cannot be delocalized onto the phenyl group, resulting in less stabilization of the carbocation intermediate.

Conclude that the phenyl group is an ortho–para director because the resonance contributors for the ortho and para positions allow for greater stabilization of the carbocation intermediate compared to the meta position.

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Key Concepts

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

Carbocation Stability

Carbocations are positively charged carbon species that are stabilized by adjacent electron-donating groups. The stability of a carbocation is crucial in determining the reactivity of electrophilic aromatic substitution reactions. A more stable carbocation intermediate leads to a more favorable reaction pathway, influencing the position of substitution on the aromatic ring.

Resonance Contributors

Resonance contributors are different Lewis structures that represent the same molecule, illustrating how electrons are delocalized across the structure. In the case of a phenyl group, resonance allows the positive charge of the carbocation to be shared with the aromatic ring, enhancing stability. This delocalization is key to understanding how substituents influence the reactivity and orientation of electrophilic attacks.

Ortho-Para Directing Effects

Ortho-para directing effects refer to the tendency of certain substituents, like phenyl groups, to direct incoming electrophiles to the ortho and para positions on an aromatic ring during substitution reactions. This is due to the resonance stabilization of the carbocation intermediates formed at these positions, which are more stable than those formed at the meta position. Understanding this directing effect is essential for predicting the outcomes of electrophilic aromatic substitutions.

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