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

1. A Review of General Chemistry

Resonance Structures

Organic Chemistry

1. A Review of General Chemistry

Resonance Structures

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6:32 minutes

Problem 11(8)

Textbook Question

a. Draw resonance contributors for the following species. Do not include structures that are so unstable that their contributions to the resonance hybrid would be negligible. Indicate which are major contributors and which are minor contributors to the resonance hybrid.
b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?
11.

Verified step by step guidance

Analyze the given structure: The molecule contains a benzene ring with a negative charge and a cyano group (-CN) attached to the ring. The negative charge indicates the presence of delocalized electrons, which can participate in resonance.

Step 1: Identify possible resonance contributors. The negative charge on the benzene ring can delocalize through the π-system of the ring. Additionally, the cyano group (-CN) is an electron-withdrawing group, which can influence the resonance contributors.

Step 2: Draw the resonance contributors. Move the negative charge around the benzene ring by shifting the π-electrons. Ensure that the cyano group remains attached to the ring and does not participate directly in the resonance.

Step 3: Evaluate the stability of each resonance contributor. Contributors where the negative charge is on more electronegative atoms (e.g., oxygen or nitrogen) or in positions that stabilize the charge (e.g., through conjugation) are major contributors. Contributors where the negative charge is on less electronegative atoms or in positions that destabilize the charge are minor contributors.

Step 4: Determine if all resonance contributors contribute equally. If the resonance contributors have similar stability (e.g., the negative charge is equally delocalized across the ring), they may contribute equally to the resonance hybrid. Otherwise, identify the major and minor contributors based on their stability.

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Key Concepts

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

Resonance Structures

Resonance structures are different Lewis structures for the same molecule that depict the same arrangement of atoms but differ in the distribution of electrons. These structures help illustrate the delocalization of electrons within a molecule, which contributes to its stability. The actual structure of the molecule is a resonance hybrid, a weighted average of all valid resonance forms, where more stable forms contribute more to the hybrid.

Major and Minor Contributors

In resonance theory, major contributors are resonance structures that are more stable and thus have a greater influence on the resonance hybrid. Factors that enhance stability include full octets, minimized formal charges, and the presence of electronegative atoms in appropriate positions. Minor contributors, on the other hand, are less stable and contribute less to the overall resonance hybrid, often due to unfavorable charge distributions or incomplete octets.

Equal Contribution of Resonance Contributors

Some resonance contributors can contribute equally to the resonance hybrid if they are all equally stable and have similar energy levels. This typically occurs when the structures have similar arrangements of electrons and atoms, leading to no significant differences in stability. Identifying such contributors is crucial for understanding the overall electronic structure and reactivity of the molecule.

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Related Practice

Textbook Question

i) Which of the following resonance structures represents the 'actual' structure of the molecule shown? (ii) Which contributes more to the resonance hybrid? (iii) Why?

(a)

(b)

(c)

Textbook Question

a. Draw resonance contributors for the following species. Do not include structures that are so unstable that their contributions to the resonance hybrid would be negligible. Indicate which are major contributors and which are minor contributors to the resonance hybrid.

b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?

10.

Textbook Question

b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?

Textbook Question

b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?

Textbook Question

Which resonance contributor in each pair makes the greater contribution to the resonance hybrid?

Textbook Question

Which is a correct statement?

A. The delocalization energy of an ester is about 18 kcal/mol, and the delocalization energy of an amide is about 10 kcal/mol.

B. The delocalization energy of an ester is about 10 kcal/mol, and the delocalization energy of an amide is about 18 kcal/mol.

Textbook Question

b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?

CH₃CH=CHOCH₃

Textbook Question

b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?

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