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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7:01 minutes

Problem 46g,h

Textbook Question

Use resonance structures to identify the areas of high and low electron density in the following compounds:
g.
h.

Verified step by step guidance

Identify the functional groups in each compound. In the first compound, there is a cyano group (CN) and an amino group (NH2). In the second compound, there is a carbonyl group (C=O) and an ether linkage (O).

For the first compound, consider the resonance structures of the cyano group. The cyano group can be represented as having a triple bond between carbon and nitrogen, with a lone pair on nitrogen. This creates a region of high electron density on the nitrogen atom.

In the first compound, the amino group (NH2) can donate electron density through resonance, increasing electron density on the adjacent carbon atom. This makes the carbon atom next to the NH2 group a region of higher electron density.

For the second compound, analyze the resonance structures of the carbonyl group. The oxygen in the carbonyl group can pull electron density towards itself due to its electronegativity, creating a partial negative charge on the oxygen and a partial positive charge on the carbon, indicating a region of low electron density on the carbon.

In the second compound, the ether oxygen can also participate in resonance by donating electron density to the adjacent carbon, creating a region of higher electron density around the oxygen atom.

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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 that depict the same arrangement of atoms but differ in the placement of electrons. They help illustrate the delocalization of electrons within a molecule, which can affect electron density and stability. In organic chemistry, resonance is crucial for understanding the distribution of electron density across a molecule.

Electron Density

Electron density refers to the probability of finding electrons in a particular region of a molecule. Areas of high electron density are typically associated with negative charges or lone pairs, while areas of low electron density are associated with positive charges or electron-deficient regions. Understanding electron density is essential for predicting reactivity and interactions in chemical compounds.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. In the given structure, the cyano group (CN) and the amino group (NH2) are functional groups that influence electron distribution and resonance. These groups can affect the electron density by either donating or withdrawing electrons, impacting the molecule's reactivity.

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Related Practice

Textbook Question

For each of these ions, draw the important resonance forms and predict which resonance form is likely to be the major contributor.

(b)

Textbook Question

For each of these ions, draw the important resonance forms and predict which resonance form is likely to be the major contributor.

(c)

Textbook Question

For each of the following compounds, draw the important resonance forms. Indicate which structures are major and minor contributors or whether they have the same energy.

(e) [CH₃C(OH)₂]⁺

(f) [CH₂CHNH]^–

Textbook Question

For each of the following compounds, draw the important resonance forms. Indicate which structures are major and minor contributors or whether they have the same energy.

(g)

(h)

Textbook Question

Use resonance structures to identify the areas of high and low electron density in the following compounds:

Textbook Question

Draw the resonance contributors of the cyclooctatrienyl dianion.

b. Which of the resonance contributors makes the smallest contribution to the hybrid?

Textbook Question

a. Draw resonance contributors for the following species, showing all the lone pairs:

b. For each species, indicate the most stable resonance contributor.

3. NO₂^-

Textbook Question

i) Which of the following resonance structures represents the 'actual' structure of the molecule shown? (ii) Which contributes more to the resonance hybrid? (iii) Why?

(a)

(b)

(c)

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