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

3. Acids and Bases

Reaction Mechanism

Organic Chemistry

3. Acids and Bases

Reaction Mechanism

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7:12 minutes

Problem 71

Textbook Question

Propose a mechanism for the rearrangement that converts an ⍺-hydroxyimine to an ⍺-aminoketone in the presence of a trace amount of acid.

Verified step by step guidance

Step 1: Protonation of the hydroxyl group (-OH) on the α-hydroxyimine occurs in the presence of trace acid (H₃O⁺). This increases the electrophilicity of the carbon atom attached to the hydroxyl group, making it more susceptible to nucleophilic attack.

Step 2: The protonated hydroxyl group (-OH₂⁺) leaves as water (H₂O), generating a carbocation at the α-carbon. This carbocation is stabilized by resonance with the imine group.

Step 3: The lone pair of electrons on the nitrogen atom of the imine group migrates to form a double bond with the α-carbon, resulting in the formation of a new bond and shifting the positive charge onto the nitrogen atom.

Step 4: A molecule of water (H₂O) attacks the positively charged nitrogen atom, leading to the formation of an intermediate where the nitrogen is bonded to both the α-carbon and a hydroxyl group.

Step 5: Deprotonation of the hydroxyl group on the nitrogen occurs, resulting in the final product: an α-aminoketone, where the α-carbon is bonded to a ketone group and the nitrogen is bonded to a hydrogen atom.

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Key Concepts

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

Hydroxyimine Structure

A-hydroxyimines are compounds containing a hydroxyl group (-OH) and an imine group (C=N) on adjacent carbon atoms. This structure is crucial for understanding the rearrangement mechanism, as the hydroxyl group can participate in protonation and subsequent reactions under acidic conditions, facilitating the conversion to an a-aminoketone.

Protonation and Acid Catalysis

In the presence of a trace amount of acid, such as H3O+, protonation of the hydroxyl group occurs, enhancing its leaving ability. This step is essential in the mechanism, as it leads to the formation of a more reactive intermediate that can rearrange to form the a-aminoketone, demonstrating the role of acid catalysis in organic reactions.

Rearrangement Mechanism

The rearrangement mechanism involves the transformation of the a-hydroxyimine to an a-aminoketone through a series of steps, including protonation, loss of water, and reorganization of the double bond. Understanding this mechanism is vital for predicting the product and the reaction pathway, highlighting the importance of structural changes in organic synthesis.

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Related Practice

Textbook Question

For practice in recognizing mechanisms, classify each reaction according to the type of mechanism you expect:

1. Free-radical chain reaction

2. Reaction involving strong bases and strong nucleophiles

3. Reaction involving strong acids and strong electrophiles.

(d)

Textbook Question

For practice in recognizing mechanisms, classify each reaction according to the type of mechanism you expect:

1. Free-radical chain reaction

2. Reaction involving strong bases and strong nucleophiles

3. Reaction involving strong acids and strong electrophiles

(c)

Textbook Question

Classify each reaction as a substitution, an elimination, or neither. Identify the leaving group in each reaction, and the nucleophile in substitutions.

Textbook Question

Classify each reaction as a substitution, an elimination, or neither. Identify the leaving group in each reaction, and the nucleophile in substitutions.

Textbook Question

Classify each reaction as a substitution, an elimination, or neither. Identify the leaving group in each reaction, and the nucleophile in substitutions.

Textbook Question

The product of the Stille coupling reaction (A) tautomerizes in a basic solution to give compound B. B spontaneously converts to C.

Textbook Question

Aluminum trichloride (AlCl₃) dissolves in ether with the evolution of a large amount of heat. (In fact, this reaction can become rather violent if it gets too warm.) Show the structure of the resulting aluminum chloride etherate complex.

Multiple Choice

Which of the following analogies best describes the induced-fit model of enzyme-substrate binding?

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