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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6:33 minutes

Problem 8g,h

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)

Verified step by step guidance

Identify the compounds given: (g) is a diketone with a negative charge on the central carbon, and (h) is an aldehyde with a negative charge on the central carbon and a cyano group.

For compound (g), consider the resonance involving the movement of electrons from the negatively charged carbon to form a double bond with one of the adjacent carbonyl carbons, while the pi electrons from the carbonyl oxygen move to the oxygen, creating a negative charge on the oxygen.

For compound (g), draw the resonance form where the negative charge is on the oxygen of one of the carbonyl groups, and the central carbon forms a double bond with the other carbonyl carbon. This form is likely a major contributor due to the stability of the negative charge on oxygen.

For compound (h), consider the resonance involving the movement of electrons from the negatively charged carbon to form a double bond with the carbon of the cyano group, while the pi electrons from the cyano nitrogen move to the nitrogen, creating a negative charge on the nitrogen.

For compound (h), draw the resonance form where the negative charge is on the nitrogen of the cyano group, and the central carbon forms a double bond with the cyano carbon. This form is likely a major contributor due to the stability of the negative charge on nitrogen.

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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 delocalization of electrons. They are used to represent molecules where the electron distribution cannot be described by a single Lewis structure. The actual structure of the molecule is a resonance hybrid, which is a weighted average of all possible resonance forms.

Major and Minor Contributors

In resonance, not all structures contribute equally to the resonance hybrid. Major contributors are those with the lowest energy, typically having full octets, minimal formal charges, and charges on atoms with appropriate electronegativity. Minor contributors have higher energy due to incomplete octets, high formal charges, or charges on less suitable atoms.

Electronegativity and Charge Distribution

Electronegativity is the tendency of an atom to attract electrons. In resonance structures, the placement of charges is influenced by electronegativity; more electronegative atoms stabilize negative charges better. Understanding this helps determine which resonance forms are more stable and thus major contributors to the resonance hybrid.

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Related Practice

Textbook Question

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

(d)

Textbook Question

For each of these ions, draw the important resonance forms and predict which resonance form is likely to be the major contributor.

(b)

Textbook Question

For each of these ions, draw the important resonance forms and predict which resonance form is likely to be the major contributor.

(c)

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

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

Draw the resonance contributors of the cyclooctatrienyl dianion.

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

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^-

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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)

Key Concepts

Resonance Structures

Major and Minor Contributors

Electronegativity and Charge Distribution

Watch next

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)