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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Problem 68(9)

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?
9.

Verified step by step guidance

Identify the species in question and determine if it has delocalized electrons. Look for features such as lone pairs, π bonds, or charges that can participate in resonance.

Draw the resonance contributors by moving electrons (using curved arrows) to show how the π electrons or lone pairs can be redistributed. Ensure that each structure follows the rules of valence and does not violate the octet rule (except for elements that can expand their octet, such as sulfur or phosphorus).

Evaluate the stability of each resonance contributor. Major contributors are typically those with a full octet on all atoms, minimal formal charges, and negative charges on more electronegative atoms. Minor contributors may have incomplete octets, more formal charges, or charges on less electronegative atoms.

Label each resonance contributor as either a major or minor contributor based on the stability analysis performed in the previous step.

For part b, analyze the resonance contributors to determine if they are all equivalent in terms of stability. If all contributors have the same structure and stability (e.g., equivalent formal charges and atom arrangements), then they contribute equally to the resonance hybrid. Otherwise, they contribute unequally.

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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 placement 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 contributors.

Major and Minor Contributors

In resonance theory, not all resonance structures contribute equally to the resonance hybrid. Major contributors are those that are more stable, typically having full octets, minimal formal charges, and favorable charge distributions. Minor contributors, on the other hand, may have significant formal charges or incomplete octets, making them less stable and thus contributing less to the overall hybrid structure.

Equally Contributing Resonance Structures

Some molecules may have resonance contributors that are equally stable, meaning they contribute equally to the resonance hybrid. This occurs when all structures have similar energy levels and stability, often seen in symmetrical molecules. Identifying such contributors is crucial for understanding the overall electronic structure and reactivity of the species in question.

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Related Practice

Textbook Question

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

Textbook Question

Draw another resonance form for each of the substituted allylic cations shown in the preceding figure, showing how the positive charge is shared by another carbon atom. In each case, state whether your second resonance form is a more important or less important resonance contributor than the first structure. (Which structure places the positive charge on the more-substituted carbon atom?)

Textbook Question

Draw the Lewis structure of azidomethane (CH₃N₃) [Show two important resonance structures.]

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?

14.

Multiple Choice

Which is NOT a valid resonance contributor of acetamide?

Multiple Choice

Based on the resonance contributors, which atom is most likely to react with an acidic proton, H⁺?

Multiple Choice

Which is the correct arrow pushing formalism to convert between the following resonance contributors?

Multiple Choice

Which resonance contributor of acetic acid actually exists?

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