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

21. Aldehydes and Ketones: Nucleophilic Addition

Hydrates

Organic Chemistry

21. Aldehydes and Ketones: Nucleophilic Addition

Hydrates

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3:23 minutes

Problem 13b

Textbook Question

Propose mechanisms for
(b) the base-catalyzed hydration of acetone to form acetone hydrate.

Verified step by step guidance

Identify the reactants and products: The reactant is acetone (CH₃COCH₃), and the product is acetone hydrate (CH₃C(OH)₂CH₃). The reaction is base-catalyzed, so a hydroxide ion (OH⁻) will play a key role in the mechanism.

Step 1: Nucleophilic attack by hydroxide ion (OH⁻): The hydroxide ion attacks the electrophilic carbonyl carbon of acetone. This is because the carbonyl carbon is partially positive due to the electronegativity of the oxygen atom. This step forms a tetrahedral intermediate where the carbonyl oxygen now carries a negative charge.

Step 2: Protonation of the negatively charged oxygen: The negatively charged oxygen in the tetrahedral intermediate abstracts a proton (H⁺) from water (H₂O), forming the acetone hydrate (CH₃C(OH)₂CH₃). This step regenerates the hydroxide ion (OH⁻), which acts as the catalyst.

Step 3: Confirm the catalytic role of the base: Since the hydroxide ion is regenerated at the end of the reaction, it acts as a catalyst and is not consumed in the overall process. This confirms the base-catalyzed nature of the reaction.

Step 4: Summarize the mechanism: The base-catalyzed hydration of acetone involves two key steps: (1) nucleophilic attack by OH⁻ on the carbonyl carbon, forming a tetrahedral intermediate, and (2) protonation of the intermediate by water to yield the hydrate product. The hydroxide ion is regenerated, completing the catalytic cycle.

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Key Concepts

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

Base-Catalyzed Hydration

Base-catalyzed hydration involves the addition of water to a carbonyl compound, facilitated by a base. In this process, the base deprotonates water to generate hydroxide ions, which then attack the electrophilic carbon of the carbonyl group. This reaction typically leads to the formation of an alcohol or hydrate, depending on the conditions and the substrate.

Mechanism of Nucleophilic Addition

The mechanism of nucleophilic addition is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophilic center, such as a carbonyl carbon. In the case of acetone hydration, the hydroxide ion acts as the nucleophile, attacking the carbonyl carbon of acetone, leading to the formation of a tetrahedral intermediate that can rearrange to form the hydrate.

Equilibrium in Hydration Reactions

Hydration reactions often reach an equilibrium state, where the forward and reverse reactions occur at the same rate. For acetone hydration, this means that the formation of acetone hydrate and the reversion to acetone and water can coexist. Understanding this equilibrium is crucial for predicting the extent of hydration under different conditions, such as concentration and temperature.

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