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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2:46 minutes

Problem 47a

Textbook Question

Each pair of structures represents two valid resonance structures. Use the arrow-pushing formalism to justify the formation of the one on the left from the one on the right.
(a)

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Identify the location of the electrons in the resonance structure on the right. Look for lone pairs, π-bonds, and formal charges that can be moved to generate the resonance structure on the left.

Determine the movement of electrons using the arrow-pushing formalism. Arrows should start from a source of electrons (lone pair or π-bond) and point toward the destination (atom or bond). Ensure that the movement follows the rules of resonance.

Check for any changes in formal charges. If electrons are moved toward an atom, its formal charge may become more negative. If electrons are moved away, its formal charge may become more positive.

Verify that the octet rule is satisfied for all atoms involved in the resonance structure. Ensure that no atom exceeds its valence shell capacity.

Redraw the resonance structure on the left, incorporating the changes made by the arrow-pushing formalism. Confirm that the two structures are valid resonance forms of the same molecule, differing only in the arrangement of electrons.

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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 the same molecule that depict the same arrangement of atoms but differ in the distribution of electrons. These structures help illustrate the delocalization of electrons within a molecule, which can stabilize it. The actual structure of the molecule is a hybrid of all possible resonance forms, contributing to its overall stability and reactivity.

Arrow-Pushing Formalism

Arrow-pushing formalism is a method used in organic chemistry to depict the movement of electrons during chemical reactions. Curved arrows indicate the direction of electron flow, showing how bonds are formed or broken. This technique is essential for visualizing mechanisms and understanding how resonance structures interconvert, as it clarifies the changes in electron density and bond formation.

Electron Delocalization

Electron delocalization refers to the distribution of electrons across multiple atoms in a molecule, rather than being localized between two specific atoms. This phenomenon is crucial in resonance structures, as it allows for the stabilization of the molecule by spreading out electron density. Delocalization can affect the reactivity and properties of compounds, making it a key concept in understanding molecular behavior.

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Related Practice

Textbook Question

Determine whether the following pairs of structures are actually different compounds or simply resonance forms of the same compounds.

Textbook Question

Determine whether the following pairs of structures are actually different compounds or simply resonance forms of the same compounds.

Textbook Question

The following compound can become protonated on any of the three nitrogen atoms. One of these nitrogens is much more basic than the others, however.

a. Draw the important resonance forms of the products of protonation on each of the three nitrogen atoms.

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.

(e)

Textbook Question

Each pair of structures represents two valid resonance structures. Use the arrow-pushing formalism to justify the formation of the one on the left from the one on the right.

(b)

Textbook Question

Draw the resonance structure that would result from the indicated movement of electrons.

(a)

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.