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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4:36 minutes

Problem 111b

Textbook Question

Draw the resonance contributors of the cyclooctatrienyl dianion.
b. Which of the resonance contributors makes the smallest contribution to the hybrid?

Verified step by step guidance

Step 1: Begin by understanding the structure of the cyclooctatrienyl dianion. Cyclooctatrienyl refers to an eight-membered ring with three alternating double bonds. The dianion indicates that the molecule has two extra electrons, which are typically delocalized within the conjugated system.

Step 2: Identify the resonance contributors. Resonance contributors are different Lewis structures that represent the delocalization of electrons in the molecule. For the cyclooctatrienyl dianion, the two extra electrons can be placed in different positions within the conjugated π-system, leading to multiple resonance structures.

Step 3: Draw each resonance structure systematically. Start by moving one pair of electrons (from the dianion) to a neighboring position, ensuring that the octet rule is satisfied for all atoms. Repeat this process to generate all possible resonance contributors.

Step 4: Evaluate the stability of each resonance contributor. Resonance structures with minimal formal charges, complete octets, and delocalized electrons are generally more stable. Structures with localized charges or disrupted conjugation contribute less to the resonance hybrid.

Step 5: Identify the resonance contributor that makes the smallest contribution to the hybrid. This is typically the structure with the most localized charges or the least delocalization of electrons, as these factors reduce stability and resonance contribution.

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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 is crucial for understanding its stability and reactivity. In the case of the cyclooctatrienyl dianion, drawing resonance contributors will show how the negative charges can be distributed across the ring.

Dianion Stability

A dianion is a species that carries two negative charges. The stability of a dianion is influenced by the ability to delocalize these charges through resonance. In cyclooctatrienyl dianion, the resonance contributors will help determine which structure is more stable and thus contributes more to the overall resonance hybrid, affecting the molecule's reactivity and properties.

Resonance Hybrid

The resonance hybrid is the actual structure of a molecule that is a weighted average of all its resonance contributors. It represents the most stable arrangement of electrons and is not a single structure but rather a combination of all possible resonance forms. In evaluating which resonance contributor makes the smallest contribution, one must consider factors like charge distribution, octet rule fulfillment, and overall stability of each structure.

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Related Practice

Textbook Question

For each of the following compounds, draw the important resonance forms. Indicate which structures are major and minor contributors or whether they have the same energy.

(e) [CH₃C(OH)₂]⁺

(f) [CH₂CHNH]^–

Textbook Question

For each of the following compounds, draw the important resonance forms. Indicate which structures are major and minor contributors or whether they have the same energy.

(g)

(h)

Textbook Question

Use resonance structures to identify the areas of high and low electron density in the following compounds:

Textbook Question

Use resonance structures to identify the areas of high and low electron density in the following compounds:

Textbook Question

a. Draw resonance contributors for the following species, showing all the lone pairs:

b. For each species, indicate the most stable resonance contributor.

3. NO₂^-

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?

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Draw the resonance contributors of the cyclooctatrienyl dianion.b. Which of the resonance contributors makes the smallest contribution to the hybrid?

Key Concepts

Resonance Structures

Dianion Stability

Resonance Hybrid

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Draw the resonance contributors of the cyclooctatrienyl dianion.
b. Which of the resonance contributors makes the smallest contribution to the hybrid?