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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5:12 minutes

Problem 60g

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.
(g)

Verified step by step guidance

Step 1: Identify the most acidic hydrogen in the molecule. The molecule contains a carbonyl group (C=O) and an alpha hydrogen adjacent to the carbonyl group. Alpha hydrogens are typically the most acidic due to the resonance stabilization of the resulting enolate ion.

Step 2: Remove the most acidic hydrogen (the alpha hydrogen) to form the conjugate base. This results in the formation of an enolate ion, where the negative charge is delocalized between the alpha carbon and the oxygen atom of the carbonyl group.

Step 3: Draw the first resonance contributor of the enolate ion. In this structure, the negative charge resides on the oxygen atom of the carbonyl group, forming a double bond between the alpha carbon and the carbonyl carbon.

Step 4: Draw the second resonance contributor of the enolate ion. In this structure, the negative charge resides on the alpha carbon, and the carbonyl group retains its double bond.

Step 5: Ensure that both resonance contributors are properly drawn, showing the delocalization of the negative charge between the oxygen atom and the alpha carbon. This resonance stabilization explains the acidity of the alpha hydrogen.

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Key Concepts

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

Acidity in Organic Molecules

Acidity in organic chemistry refers to the ability of a molecule to donate a proton (H+). The most acidic hydrogens are typically found on functional groups such as carboxylic acids, alcohols, and phenols. In the provided molecule, the hydrogen attached to the carbon adjacent to the carbonyl group is the most acidic due to the electron-withdrawing effect of the carbonyl, which stabilizes the resulting anion.

Resonance Structures

Resonance structures are different ways of drawing a molecule that represent the same compound, showing the delocalization of electrons. In the context of the anion formed after deprotonation, resonance contributors illustrate how the negative charge can be distributed across multiple atoms, enhancing the stability of the anion. This concept is crucial for predicting the behavior of the anion in chemical reactions.

Stability of Anions

The stability of anions is influenced by factors such as electronegativity, resonance, and inductive effects. Anions that can delocalize their negative charge through resonance are generally more stable than those that cannot. In the case of the anion formed from the most acidic hydrogen in the given molecule, resonance with the adjacent carbonyl group significantly stabilizes the anion, making it more favorable for deprotonation.

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Related Practice

Open Question

LDA can be used to form enolates on esters and nitriles. Predict the product of these alkylation reactions.

(a)

Textbook Question

Identify the enolate(s) that would form on treatment of each of the following carbonyls with base. [When there are two possibilities, draw both.]

(a)

Textbook Question

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

Textbook Question

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

(d) nitroacetone

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)

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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.(g)

Key Concepts

Acidity in Organic Molecules

Resonance Structures

Stability of Anions

Watch next

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.
(g)