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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6:15 minutes

Problem 24

Textbook Question

How many atoms share the unpaired electron in semiquinone?

Verified step by step guidance

Step 1: Recognize the structure of semiquinone. Semiquinone is a radical species derived from quinones, where one of the oxygen atoms has an unpaired electron. The structure provided shows a benzene ring with an oxygen atom attached, carrying an unpaired electron.

Step 2: Understand the delocalization of the unpaired electron. In semiquinone, the unpaired electron is not localized on the oxygen atom alone but is delocalized over the conjugated π-system of the benzene ring and the oxygen atom.

Step 3: Analyze the conjugated system. The benzene ring has alternating double bonds, which form a conjugated π-system. The oxygen atom is connected to the ring, allowing the unpaired electron to interact with the π-system.

Step 4: Determine the atoms involved in delocalization. The delocalization occurs over the oxygen atom and the carbon atoms of the benzene ring that are part of the conjugated π-system. This includes the oxygen atom and six carbon atoms of the benzene ring.

Step 5: Conclude the number of atoms sharing the unpaired electron. The unpaired electron is shared among seven atoms: the oxygen atom and the six carbon atoms of the benzene ring.

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Key Concepts

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

Radicals

Radicals are species that contain unpaired electrons, making them highly reactive. In organic chemistry, they often participate in various reactions, including addition and substitution. Understanding the nature of radicals is crucial for analyzing their stability and reactivity, particularly in compounds like semiquinone, which features an unpaired electron.

Semiquinone Structure

Semiquinones are a class of organic compounds derived from quinones, characterized by having one unpaired electron. This unpaired electron can be localized on one of the carbon atoms in the ring structure, influencing the compound's chemical behavior. Recognizing the specific atom that holds the unpaired electron is essential for understanding the properties and reactivity of semiquinones.

Electron Delocalization

Electron delocalization refers to the distribution of electrons across multiple atoms in a molecule, which can stabilize radicals and influence their reactivity. In semiquinones, the unpaired electron may be delocalized over the aromatic ring, affecting the overall stability and reactivity of the compound. This concept is vital for predicting how semiquinones will interact in chemical reactions.

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Related Practice

Textbook Question

Draw resonance contributors for each of the following species and rank them in order of decreasing contribution to the resonance hybrid. Then draw the resonance hybrid.

Textbook Question

Draw resonance contributors for each of the following species and rank them in order of decreasing contribution to the resonance hybrid. Then draw the resonance hybrid.

Textbook Question

Which of the following has delocalized electrons?

Textbook Question

Draw all resonance structures of the following carbanion and carbocation.

(a)

(b)

Textbook Question

Draw the resonance contributors for the following radicals:

Textbook Question

Another way the preceding might be presented is to say that the minor resonance structure(s) reveal the reactivity of a molecule. Show how the minor resonance structure(s) can help us understand that the following reactions occur with the regioselectivity shown.

(a)

(b)

(c)

Textbook Question

A carboxylic acid has two oxygen atoms, each with two nonbonding pairs of electrons.

(a) Draw the resonance forms of a carboxylic acid that is protonated on the hydroxy oxygen atom.

(b) Compare the resonance forms with those given previously for an acid protonated on the carbonyl oxygen atom.

Textbook Question

Draw the resonance contributors of the peptide bond in the less stable configuration.

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