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

16. Conjugated Systems

Stability of Conjugated Intermediates

Organic Chemistry

16. Conjugated Systems

Stability of Conjugated Intermediates

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2:14 minutes

Problem 27b

Textbook Question

Draw the important resonance contributors for the following cations, anions, and radicals.
(b)

Verified step by step guidance

Identify the structure of the given species (cation, anion, or radical) and locate any atoms with lone pairs, π-bonds, or unfilled octets. These features are key to determining resonance contributors.

Determine the movement of electrons. For resonance structures, electrons can move in the form of lone pairs or π-bonds. Use curved arrows to show the movement of electrons from one location to another.

Draw the new resonance structure after the electron movement. Ensure that the formal charges on atoms are updated correctly based on the electron redistribution.

Repeat the process to identify all possible resonance contributors. Remember that resonance structures must follow the rules of valence and cannot violate the octet rule (except for elements that can expand their octet, such as sulfur or phosphorus).

Evaluate the stability of each resonance structure. More stable contributors will have minimal formal charges, complete octets, and place negative charges on more electronegative atoms or positive charges on less electronegative atoms.

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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 or ion that show the same arrangement of atoms but differ in the placement of electrons. These structures help illustrate the delocalization of electrons within a molecule, which can stabilize cations, anions, and radicals. Understanding resonance is crucial for predicting the reactivity and stability of these species.

Cation Stability

Cations are positively charged species formed by the loss of electrons. Their stability is influenced by factors such as the ability to delocalize positive charge through resonance and the electronegativity of surrounding atoms. More stable cations typically have resonance contributors that distribute the positive charge over multiple atoms, reducing the energy of the species.

Radical Stability

Radicals are species with unpaired electrons, making them highly reactive. The stability of radicals can be enhanced through resonance, where the unpaired electron can be delocalized over adjacent atoms. This delocalization lowers the energy of the radical and makes it less reactive, which is essential for understanding their behavior in chemical reactions.

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