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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Problem 64f

Textbook Question

Two resonance structures are shown for each molecule. Use the arrow-pushing formalism to represent the electron flow from the structure on the left to the one on the right.
(f)

Verified step by step guidance

Step 1: Identify the resonance structures provided in the problem. Resonance structures differ in the placement of electrons, specifically π-electrons and lone pairs, while the arrangement of atoms remains the same.

Step 2: Locate the regions in the molecule where electron movement occurs. Typically, this involves π-bonds, lone pairs, or formal charges. Look for areas where electrons can delocalize to stabilize the molecule.

Step 3: Use curved arrows to represent the movement of electrons. A curved arrow starts at the source of electrons (a lone pair or a bond) and points to where the electrons are moving. Ensure the arrows follow the rules of electron flow: electrons move from areas of high electron density to areas of lower electron density.

Step 4: Verify that the resulting resonance structure adheres to the rules of resonance. The connectivity of atoms must remain unchanged, and the total number of electrons must be conserved. Ensure that formal charges are correctly assigned in the new structure.

Step 5: Confirm that the resonance structures are valid and contribute to the resonance hybrid. Resonance structures should differ only in the placement of electrons, not the arrangement of atoms, and should follow the octet rule where applicable.

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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 ways of drawing the same molecule that illustrate the delocalization of electrons. They are used to represent molecules that cannot be accurately depicted by a single Lewis structure. Each resonance structure contributes to the overall hybrid structure, which is a more accurate representation of the molecule's electron distribution.

Arrow-Pushing Formalism

Arrow-pushing formalism is a method used in organic chemistry to depict the movement of electrons during chemical reactions. Arrows indicate the direction of electron flow, with a double-headed arrow showing the movement of a pair of electrons and a single-headed arrow indicating the movement of a single electron. This technique helps visualize how bonds are formed and broken in chemical transformations.

Electron Delocalization

Electron delocalization refers to the phenomenon where electrons are spread over several atoms rather than being localized between two atoms. This occurs in resonance structures, where the electrons can occupy multiple positions, leading to increased stability of the molecule. Delocalization is a key factor in understanding the reactivity and properties of organic compounds.

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Related Practice

Textbook Question

For each of the molecules shown, do the following:

(i) Identify all pushable pairs.

(ii) Identify all places where electrons can be pushed.

(iii) Draw one valid resonance structure.

(a)

Textbook Question

In the following molecules, identify all pushable electron pairs.

(a)

Textbook Question

Two resonance structures are shown for each molecule. Use the arrow-pushing formalism to represent the electron flow from the structure on the left to the one on the right.

(b)

Textbook Question

Two resonance structures are shown for each molecule. Use the arrow-pushing formalism to represent the electron flow from the structure on the left to the one on the right.

(d)

Textbook Question

Identify the resonance structure that will be produced given the molecule shown and the electron flow indicated.

(a)

Textbook Question

Identify the resonance structure that will be produced given the molecule shown and the electron flow indicated.

(c)

Textbook Question

Draw the important resonance forms of the following free radicals.

(c)

(d)

Textbook Question