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

16. Conjugated Systems

Stability of Conjugated Intermediates

Organic Chemistry

16. Conjugated Systems

Stability of Conjugated Intermediates

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6:10 minutes

Problem 27e,f

Textbook Question

Draw the important resonance contributors for the following cations, anions, and radicals.
(e)
(f)

Verified step by step guidance

Step 1: Identify the resonance contributors by analyzing the structure. For the first molecule (e), the negative charge on the CH2 group can delocalize through the conjugated π-system. This involves the movement of electrons along the double bonds and towards the carbonyl group.

Step 2: Draw the first resonance structure for molecule (e) by moving the lone pair of electrons from the negatively charged CH2 group to form a double bond with the adjacent carbon. This will push the electrons in the existing double bond towards the next carbon in the chain.

Step 3: Continue the electron movement for molecule (e) by shifting the electrons in the conjugated π-system further down the chain, eventually reaching the carbonyl group. The oxygen in the carbonyl group can accept the electrons, forming a resonance structure with a negative charge on the oxygen.

Step 4: For the second molecule (f), analyze the aromatic ring and the carboxylate group. The negative charge on the oxygen can delocalize into the aromatic ring, forming resonance structures. This involves the movement of electrons from the oxygen into the ring, creating alternating double bonds and redistributing the negative charge.

Step 5: Draw additional resonance structures for molecule (f) by moving the electrons around the aromatic ring. Ensure that the negative charge is delocalized across the ring and that the aromaticity of the ring is preserved in all resonance contributors.

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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 placement of electrons. These structures help illustrate the delocalization of electrons within a molecule, which can stabilize cations, anions, and radicals. Understanding resonance is crucial for predicting the reactivity and stability of these species.

Stability of Resonance Contributors

Not all resonance structures contribute equally to the overall resonance hybrid; some are more stable than others. Factors influencing stability include the octet rule, charge distribution, and the presence of formal charges. More stable resonance contributors have full octets, minimized formal charges, and charge separation that aligns with electronegativity trends.

Electrophiles and Nucleophiles

In organic chemistry, electrophiles are electron-deficient species that seek electrons, while nucleophiles are electron-rich species that donate electrons. Understanding the nature of these species is essential when analyzing resonance structures, as it helps predict how cations, anions, and radicals will interact in chemical reactions. This knowledge is fundamental for grasping reaction mechanisms and stability.

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Related Practice

Textbook Question

Draw the important resonance contributors for the following cations, anions, and radicals.

(a)

Textbook Question

Draw the important resonance contributors for the following cations, anions, and radicals.

(b)

Textbook Question

Draw the important resonance contributors for the following cations, anions, and radicals.

(c)

Textbook Question

Draw the important resonance contributors for the following cations, anions, and radicals.

(d)

Textbook Question

Which of the double bonds in zingiberene, the compound responsible for the aroma of ginger, is most reactive in an electrophilic addition reaction with HBr?

Textbook Question

The benzene ring alters the reactivity of a neighboring group in the benzylic position much as a double bond alters the reactivity of groups in the allylic position.

Benzylic cations, anions, and radicals are all more stable than simple alkyl intermediates.

a. Use resonance forms to show the delocalization (over four carbon atoms) of the positive charge of the benzyl cation.

Textbook Question

The benzene ring alters the reactivity of a neighboring group in the benzylic position much as a double bond alters the reactivity of groups in the allylic position.

Benzylic cations, anions, and radicals are all more stable than simple alkyl intermediates.

a. Use resonance forms to show the delocalization (over four carbon atoms) of the unpaired electron of the benzyl radical.

Textbook Question

The benzene ring alters the reactivity of a neighboring group in the benzylic position much as a double bond alters the reactivity of groups in the allylic position.

Benzylic cations, anions, and radicals are all more stable than simple alkyl intermediates.

c. Which of the following reactions will have the faster rate and give the better yield? Use a drawing of the transition state to explain your answer.

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Draw the important resonance contributors for the following cations, anions, and radicals.(e) (f)

Key Concepts

Resonance Structures

Stability of Resonance Contributors

Electrophiles and Nucleophiles

Watch next

Draw the important resonance contributors for the following cations, anions, and radicals.
(e)
(f)