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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6:53 minutes

Problem 44b

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)

Verified step by step guidance

Identify the ion in the structure: The given structure is a benzyl anion, where the negative charge is located on the CH2 group attached to the benzene ring.

Draw the first resonance structure: Move the lone pair of electrons from the negatively charged carbon to form a double bond with the adjacent carbon atom in the benzene ring. This will push the electrons in the adjacent double bond towards the next carbon atom, creating a new resonance structure.

Draw the second resonance structure: Continue the electron movement by pushing the electrons from the newly formed double bond to the next carbon-carbon double bond in the benzene ring, creating another resonance structure with the negative charge now on a different carbon atom in the ring.

Draw the third resonance structure: Repeat the electron movement process to push the electrons from the current double bond to the next carbon-carbon double bond, resulting in a resonance structure with the negative charge on yet another carbon atom in the benzene ring.

Predict the major contributor: Evaluate the resonance structures based on stability. The major contributor is typically the one where the negative charge is on the most electronegative atom or the one that maintains aromaticity. In this case, the structure that maintains the aromaticity of the benzene ring and has the negative charge on the CH2 group is likely the major contributor.

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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 a molecule that depict the same arrangement of atoms but differ in the distribution of electrons. They are used to represent delocalized electrons within certain molecules where the bonding cannot be expressed by a single Lewis structure. The true structure is a hybrid of all possible resonance forms, contributing to the molecule's stability.

Major Resonance Contributor

The major resonance contributor is the resonance structure that most accurately represents the molecule's electron distribution. It typically has the lowest energy, which is achieved by minimizing formal charges, maximizing covalent bonds, and placing negative charges on more electronegative atoms. This structure contributes most to the resonance hybrid, influencing the molecule's properties.

Electronegativity and Charge Distribution

Electronegativity is the tendency of an atom to attract electrons towards itself. In resonance structures, the distribution of charges is influenced by electronegativity, with negative charges preferably residing on more electronegative atoms like oxygen. This affects the stability of resonance forms, as structures with charges on appropriate atoms are more stable and likely to be major contributors.

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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:

(c)

Textbook Question

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

(a)

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.

(d) [H₂CNO₂]^–

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.

(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

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:

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