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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4:27 minutes

Problem 55a

Textbook Question

Draw the products of the following reactions:
a.

Verified step by step guidance

Step 1: Identify the starting material, which is a ketone with a cyclopentane ring and a methyl group attached to the carbonyl carbon.

Step 2: Recognize the reagents used in the reaction. LDA (Lithium Diisopropylamide) is a strong, non-nucleophilic base, and THF (tetrahydrofuran) is the solvent. The reaction is performed at -78°C, which favors kinetic enolate formation.

Step 3: Understand the mechanism. LDA will deprotonate the most accessible alpha-hydrogen (hydrogen on the carbon adjacent to the carbonyl group) to form the kinetic enolate. The kinetic enolate is formed on the less substituted alpha-carbon due to steric hindrance.

Step 4: Analyze the second step. D₂O (deuterium oxide) is added, which will replace the enolate's alpha-hydrogen with a deuterium atom through protonation of the enolate intermediate.

Step 5: Draw the product. The final product will be the original ketone structure with a deuterium atom replacing the alpha-hydrogen on the less substituted alpha-carbon.

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Key Concepts

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

Enolate Formation

Enolate formation is a key reaction in organic chemistry where a base abstracts a proton from an alpha carbon of a carbonyl compound, resulting in the formation of an enolate ion. This ion is resonance-stabilized and can act as a nucleophile in subsequent reactions. In the given reaction, LDA (Lithium diisopropylamide) is used as a strong base to generate the enolate at low temperatures, which is crucial for controlling the reaction pathway.

Aldol Reaction

The aldol reaction involves the condensation of two carbonyl compounds, typically aldehydes or ketones, to form a β-hydroxy carbonyl compound. In this case, the enolate formed in the first step can attack another carbonyl carbon, leading to the formation of a new carbon-carbon bond. This reaction is fundamental in building complex organic molecules and is often followed by dehydration to yield α,β-unsaturated carbonyl compounds.

Deuterium Incorporation

Deuterium incorporation refers to the introduction of deuterium (D or ²H), a stable isotope of hydrogen, into organic molecules. In the second step of the reaction, D₂O is used, allowing the enolate to react with deuterium instead of regular hydrogen. This process is significant in labeling studies and mechanistic investigations, as it can provide insights into reaction pathways and the behavior of intermediates.

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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)

Textbook Question

Phenylacetone can form two different enols.

(a) Show the structures of these enols.

(b) Predict which enol will be present in the larger concentration at equilibrium.

Textbook Question

For each molecule shown below,

1. indicate the most acidic hydrogens.

(a)

(b)

(c)

Textbook Question

Draw the products of the following reactions:

Textbook Question

Alkylation of the following compound with methyl iodide under two different conditions forms two different ketoesters (A and B). Each ketoester forms a cyclic diketone (C and D) when treated with methoxide ion in methanol. a. Draw the structures of A and B, and indicate the conditions used in the alkylation reaction that cause that ketoester to be formed.

Textbook Question

2. Indicate which compounds would be more than 99% deprotonated by a solution of sodium ethoxide in ethanol.

Textbook Question

For each molecule shown below,

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

(a)

(b)

(c)

Textbook Question

1. Rank the following compounds in order of increasing acidity.

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