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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4:11 minutes

Problem 61g,h,i

Textbook Question

Which of the following has delocalized electrons?
g.
h.
i.

Verified step by step guidance

Step 1: Understand the concept of delocalized electrons. Delocalized electrons are electrons that are not confined to a single atom or bond but are spread across multiple atoms, typically in conjugated systems or resonance structures.

Step 2: Analyze structure (a). Structure (a) contains alternating double bonds (a conjugated system) and a positively charged carbon atom. The conjugated system allows for delocalization of π-electrons across the double bonds.

Step 3: Analyze structure (b). Structure (b) has a positively charged carbon atom, but the double bonds are not conjugated (they are separated by a single bond). This lack of conjugation prevents delocalization of electrons.

Step 4: Analyze structure (c). Structure (c) contains a nitrogen atom with a lone pair and a double bond nearby. However, the lone pair on nitrogen is not part of a conjugated system, and the double bond does not interact with the lone pair to create delocalization.

Step 5: Conclude that structure (a) has delocalized electrons due to the conjugated system, while structures (b) and (c) do not exhibit delocalization of electrons.

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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 but are spread over several atoms. This phenomenon occurs in molecules with conjugated systems or resonance structures, where electrons can move freely between multiple bonding sites, contributing to the stability and reactivity of the molecule.

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. The true structure is a blend of these forms, leading to increased stability.

Conjugation

Conjugation refers to the overlap of p-orbitals across adjacent double or triple bonds, allowing for the delocalization of electrons. This arrangement stabilizes the molecule and can affect its reactivity and color. Conjugated systems are often found in organic compounds, such as dyes and pigments, where they contribute to unique properties.

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Related Practice

Textbook Question

Allylic halides have the structure

b. Draw the resonance structures of the allylic cations formed by ionization of the following halides.

(i)

(ii)

Textbook Question

3-Bromocyclohexene is a secondary halide. It undergoes S_N1 substitution about as fast as most tertiary halides. Use resonance structures to explain this enhanced reactivity.

Textbook Question

Benzyl bromide is a primary halide. It undergoes S_N1 substitution about as fast as most tertiary halides. Use resonance structures to explain this enhanced reactivity.

Textbook Question

Are the following pairs of structures resonance contributors or different compounds?

Textbook Question

Draw the resonance contributors for phenol.

Textbook Question

Draw the resonance contributors for the phenolate ion.

Textbook Question

Draw resonance contributors for the following ions:

Textbook Question

a. Predict the relative bond lengths of the three carbon–oxygen bonds in the carbonate ion.

b. What is the charge on each oxygen?

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