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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3:46 minutes

Problem 61j,k,l

Textbook Question

Which of the following has delocalized electrons?
j.
k.
l.

Verified step by step guidance

Analyze the structures provided: Structure j is a cyclopentadienyl cation, structure k is benzene, and structure l is cyclohexadiene.

Delocalized electrons are electrons that are shared across multiple atoms, typically in conjugated systems with alternating single and double bonds or in aromatic systems.

For structure j (cyclopentadienyl cation), the positive charge and the conjugated double bond system allow for delocalization of π-electrons across the ring, making it aromatic.

For structure k (benzene), the alternating double bonds form a fully conjugated π-electron system, which is delocalized over the entire ring, making it aromatic.

For structure l (cyclohexadiene), the double bonds are not fully conjugated (there is a single bond separating them), so the π-electrons are not delocalized across the entire ring.

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Key Concepts

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

Delocalized Electrons

Delocalized electrons are electrons that are not associated with a single atom or a single bond. Instead, they are spread over several atoms, allowing for resonance structures in molecules. This phenomenon is commonly observed in conjugated systems, such as benzene, where the electrons in the pi bonds can move freely across the ring, contributing to the stability and unique properties of the compound.

Resonance Structures

Resonance structures are different ways of drawing the same molecule that illustrate the delocalization of electrons. These structures help chemists understand the actual electron distribution in a molecule, which is often a hybrid of the resonance forms. For example, benzene can be represented by multiple resonance structures, indicating that the electrons are shared among all carbon atoms, leading to equal bond lengths.

Aromaticity

Aromaticity is a property of cyclic compounds that have a planar structure, complete delocalization of pi electrons, and follow Hückel's rule (4n + 2 pi electrons). Aromatic compounds, like benzene, exhibit enhanced stability due to this delocalization, which lowers their energy compared to non-aromatic compounds. This concept is crucial for understanding the behavior and reactivity of many organic molecules.

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Related Practice

Textbook Question

Draw the resonance contributors for the following radicals:

Textbook Question

Draw the resonance contributors for the following radicals:

Textbook Question

The given was missing some important resonance forms of the intermediates shown in brackets. Complete this mechanism by drawing all the resonance forms of these intermediates. Do your resonance forms help to explain why this reaction occurs under very mild conditions (water with a tiny trace of acid)?

Textbook Question

All of the rings of the four heterocyclic bases are aromatic. This is more apparent when the polar resonance forms of the amide groups are drawn, as is done for thymine here. Redraw the hydrogen-bonded guanine-cytosine and adenine-thymine pairs shown in Figure 23-24, using the polar resonance forms of the amides. Show how these forms help to explain why the hydrogen bonds involved in these pairings are particularly strong. Remember that a hydrogen bond arises between an electron-deficient hydrogen atom and an electron-rich pair of nonbonding electrons.

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.

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]^–

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Which of the following has delocalized electrons?j. k. l.

Key Concepts

Delocalized Electrons

Resonance Structures

Aromaticity

Watch next

Which of the following has delocalized electrons?
j.
k.
l.