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

Tautomers of Dicarbonyl Compounds

Organic Chemistry

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Tautomers of Dicarbonyl Compounds

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4:42 minutes

Problem 7d,e

Textbook Question

Draw the enol tautomers for each of the following compounds. For compounds that have more than one enol tautomer, indicate the one that is more stable.
d.
e.

Verified step by step guidance

Step 1: Understand the concept of keto-enol tautomerism. Keto-enol tautomerism is a chemical equilibrium between a ketone (or aldehyde) and its corresponding enol form. The enol form involves a hydroxyl group (-OH) attached to a carbon-carbon double bond.

Step 2: Analyze the first compound (cyclohexane-1,3-dione). Identify the alpha-hydrogens (hydrogens attached to the carbon adjacent to the carbonyl group). These hydrogens are necessary for enol formation. In this case, both carbonyl groups have alpha-hydrogens available.

Step 3: Draw the enol tautomers for the first compound. For each carbonyl group, the alpha-hydrogen can be removed, and the resulting negative charge can form a double bond with the adjacent carbon. The oxygen of the carbonyl group will then gain a proton to form the hydroxyl group. Consider resonance stabilization to determine the most stable enol tautomer.

Step 4: Analyze the second compound (2,4-pentanedione). This compound has two carbonyl groups separated by a single carbon atom. Identify the alpha-hydrogens on the central carbon atom. These hydrogens can be removed to form enol tautomers. The enol tautomer with intramolecular hydrogen bonding is typically more stable due to resonance stabilization.

Step 5: Draw the enol tautomers for the second compound. Remove the alpha-hydrogens from the central carbon atom, form a double bond between the central carbon and one of the adjacent carbons, and add a hydroxyl group to the oxygen of the carbonyl group. Indicate the tautomer with intramolecular hydrogen bonding as the more stable form.

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Key Concepts

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

Tautomerism

Tautomerism is a chemical phenomenon where two or more isomers, known as tautomers, exist in dynamic equilibrium, typically differing in the position of a proton and a double bond. In organic chemistry, the most common type is keto-enol tautomerism, where a ketone or aldehyde (keto form) can convert to an enol form, characterized by a hydroxyl group bonded to a carbon-carbon double bond.

Enol Stability

The stability of enol tautomers is influenced by factors such as hydrogen bonding, sterics, and resonance. Generally, enols are less stable than their keto counterparts due to the presence of a double bond and a hydroxyl group, which can lead to increased strain. However, certain enols can be stabilized by intramolecular hydrogen bonding or resonance effects, making them more favorable in specific contexts.

Drawing Tautomers

When drawing tautomers, it is essential to accurately depict the structural changes that occur during the tautomerization process. This includes the movement of protons and the formation or breaking of double bonds. Understanding the molecular structure and functional groups present in the compound is crucial for correctly identifying and illustrating the enol forms and determining their relative stability.

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