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

Tautomerization

Organic Chemistry

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Tautomerization

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2:02 minutes

Problem 1c3

Textbook Question

Phenylacetone can form two different enols.
(c) Propose mechanisms for the formation of the first enol in base.

Verified step by step guidance

Identify the structure of phenylacetone: It is a ketone with a phenyl group attached to the alpha-carbon. The molecular structure can be represented as C6H5-CH2-CO-CH3.

Understand the concept of enol formation: Enols are formed when a hydrogen atom from the alpha-carbon (the carbon adjacent to the carbonyl group) is removed, and the resulting negative charge is delocalized to form a double bond between the alpha-carbon and the carbonyl carbon, while the oxygen of the carbonyl group gains a proton to form an -OH group.

Initiate the mechanism in base: A strong base (e.g., hydroxide ion, OH⁻) abstracts an acidic proton from the alpha-carbon of phenylacetone. This generates a resonance-stabilized enolate ion.

Illustrate resonance stabilization: The enolate ion has two resonance forms. In one form, the negative charge is on the alpha-carbon, and in the other, the negative charge is delocalized onto the oxygen atom of the carbonyl group. This delocalization stabilizes the intermediate.

Complete the enol formation: The enolate ion reacts with a proton donor (e.g., water) to protonate the oxygen atom, forming the enol. The final structure of the enol will have a double bond between the alpha-carbon and the carbonyl carbon, and the oxygen will be part of a hydroxyl (-OH) group.

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Key Concepts

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

Enol Formation

Enol formation involves the conversion of a carbonyl compound, such as a ketone or aldehyde, into its corresponding enol form, which features a double bond between a carbon and an adjacent carbon with a hydroxyl group. This process is significant in organic chemistry as enols can participate in various reactions, including tautomerization and electrophilic addition.

Base-Catalyzed Mechanism

In a base-catalyzed mechanism, a base abstracts a proton from the carbon adjacent to the carbonyl group, generating a carbanion. This carbanion can then attack the carbonyl carbon, leading to the formation of the enolate ion, which can subsequently rearrange to form the enol. Understanding this mechanism is crucial for predicting the products of reactions involving carbonyl compounds.

Tautomerization

Tautomerization is a chemical reaction that involves the interconversion between two isomers, typically a keto form and an enol form. This process is often facilitated by the presence of acids or bases and is important in understanding the stability and reactivity of different isomers in organic compounds, including phenylacetone.

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Phenylacetone can form two different enols.(c) Propose mechanisms for the formation of the first enol in base.

Key Concepts

Enol Formation

Base-Catalyzed Mechanism

Tautomerization

Watch next

Phenylacetone can form two different enols.
(c) Propose mechanisms for the formation of the first enol in base.