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

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Enolate

Organic Chemistry

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Enolate

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2:28 minutes

Problem 3f

Textbook Question

Give the important resonance forms for the possible enolate ions of the following:
(f)

Verified step by step guidance

Identify the alpha hydrogens in the molecule. Alpha hydrogens are the hydrogens attached to the carbon atoms adjacent to the carbonyl group. In this case, the molecule is a ketone, and the alpha hydrogens are present on the carbons adjacent to the carbonyl carbon.

Determine the possible enolate ions that can form. Deprotonation of an alpha hydrogen by a base leads to the formation of an enolate ion. The enolate ion consists of a negatively charged oxygen atom and a double bond between the alpha carbon and the carbonyl carbon.

Draw the resonance forms of the enolate ion. The negative charge on the oxygen can delocalize to the alpha carbon, forming a resonance structure where the double bond shifts between the alpha carbon and the carbonyl carbon. Use curved arrows to show the movement of electrons.

Consider the stability of the resonance forms. Resonance structures that place the negative charge on the more electronegative atom (oxygen) are generally more stable. However, both resonance forms contribute to the overall stability of the enolate ion.

Repeat the process for all possible alpha carbons in the molecule. In this case, there are two alpha carbons (one on each side of the carbonyl group), so you will need to draw resonance forms for enolate ions formed from deprotonation at each alpha carbon.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Enolate Ions

Enolate ions are reactive intermediates formed from the deprotonation of a carbonyl compound, typically a ketone or aldehyde. They contain a negatively charged carbon atom adjacent to a carbonyl group, which allows for resonance stabilization. This resonance can lead to different structural forms, influencing the reactivity and stability of the enolate in various reactions.

Resonance Structures

Resonance structures are different Lewis structures for the same molecule that depict the delocalization of electrons. In the case of enolate ions, resonance allows the negative charge to be shared between the carbon atom and the oxygen atom of the carbonyl group. This delocalization stabilizes the enolate ion and is crucial for understanding its reactivity in organic reactions.

Carbonyl Compounds

Carbonyl compounds, characterized by the presence of a carbon-oxygen double bond (C=O), include aldehydes, ketones, and carboxylic acids. They are key players in organic chemistry due to their electrophilic nature, which allows them to participate in various reactions, including nucleophilic addition and enolate formation. Understanding their structure and reactivity is essential for analyzing enolate ions and their resonance forms.

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Related Practice

Textbook Question

For each molecule shown below,

1. indicate the most acidic hydrogens.

2. draw the important resonance contributors of the anion that results from removal of the most acidic hydrogen.

(h)

Textbook Question

Give the important resonance forms for the possible enolate ions of the following:

Textbook Question

Give the important resonance forms for the possible enolate ions of the following:

(d)

Textbook Question

Give the important resonance forms for the possible enolate ions of the following:

(e)

Textbook Question

Show the resonance forms for the enolate ions that result when the following compounds are treated with a strong base.

(a) ethyl acetoacetate

(b) pentane-2,4-dione

Textbook Question

When cis-2,4-dimethylcyclohexanone is dissolved in aqueous ethanol containing a trace of NaOH, a mixture of cis and trans isomers results. Propose a mechanism for this isomerization.

Textbook Question

For each molecule shown below,

1. indicate the most acidic hydrogens.

2. draw the important resonance contributors of the anion that results from removal of the most acidic hydrogen.

(d)

Textbook Question

For each molecule shown below,

1. indicate the most acidic hydrogens.

2. draw the important resonance contributors of the anion that results from removal of the most acidic hydrogen.

(e)

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