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

26. Amines

Reductive Amination

Organic Chemistry

26. Amines

Reductive Amination

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8:07 minutes

Problem 46a

Textbook Question

Propose mechanisms for the following reactions.
(a)

Verified step by step guidance

Step 1: Analyze the starting material and reagents. The starting material is cyclopentanone, a ketone. The reagents include dimethylamine (NH(CH3)2) in the presence of acid (H+), followed by sodium triacetoxyborohydride (NaBH(OAc)3) in acetic acid (CH3COOH). This suggests an imine formation followed by reduction.

Step 2: Imine formation. The ketone reacts with dimethylamine under acidic conditions. The oxygen of the ketone is protonated by H+, increasing the electrophilicity of the carbonyl carbon. Dimethylamine then attacks the carbonyl carbon, forming a tetrahedral intermediate. This intermediate loses water to form an imine (C=N bond).

Step 3: Reduction of the imine. Sodium triacetoxyborohydride (NaBH(OAc)3) is a mild reducing agent that selectively reduces imines to amines. The imine formed in the previous step is reduced to a secondary amine, where the nitrogen is bonded to two methyl groups and the cyclopentyl group.

Step 4: Protonation and stabilization. The reaction occurs in acetic acid, which helps stabilize intermediates and ensures the reaction proceeds smoothly. The final product is a secondary amine with the structure shown in the image.

Step 5: Verify the mechanism. Ensure that all steps follow proper electron movement and that the reagents used are consistent with the transformations observed in the reaction. The final product is a secondary amine derived from cyclopentanone and dimethylamine.

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Key Concepts

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

Reductive Amination

Reductive amination is a chemical reaction that involves the conversion of a carbonyl compound (like an aldehyde or ketone) into an amine. This process typically occurs in two steps: first, the carbonyl compound reacts with an amine to form an imine or enamine, followed by reduction to yield the amine. The use of reducing agents, such as sodium borohydride (NaBH4), is crucial in the second step to facilitate the reduction.

Mechanism of Imine Formation

The formation of an imine from a carbonyl compound and an amine involves nucleophilic attack by the amine on the carbonyl carbon, leading to the formation of a tetrahedral intermediate. This intermediate then undergoes dehydration, releasing water and forming the imine. Understanding this mechanism is essential for predicting the behavior of the reactants and the conditions required for successful reaction completion.

Role of Reducing Agents

Reducing agents are substances that donate electrons to another species, reducing its oxidation state. In the context of reductive amination, sodium borohydride (NaBH4) is commonly used to reduce the imine to the corresponding amine. The choice of reducing agent can significantly affect the reaction's efficiency and selectivity, making it important to understand their properties and reactivity in organic synthesis.

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Related Practice

Textbook Question

The compounds commonly known as 'amino acids' are actually α-aminocarboxylic-aminocarboxylic acids. What carbonyl compounds should be used to synthesize the two amino acids shown here?

Textbook Question

The compounds commonly known as 'amino acids' are actually α-aminocarboxylic-aminocarboxylic acids. What carbonyl compounds should be used to synthesize the two amino acids shown here?

Textbook Question

Excess ammonia must be used when a primary amine is synthesized by reductive amination. What product will be obtained if the reaction is carried out with excess carbonyl compound?

Textbook Question

The two most general amine syntheses are the reductive amination of carbonyl compounds and the reduction of amides. Show how these techniques can be used to accomplish the following syntheses.

(b) benzaldehyde → benzylamine

Textbook Question

Show how to synthesize the following amines from the indicated starting materials by reductive amination.

(a) benzylmethylamine from benzaldehyde

(b) N-benzylpiperidine from piperidine

Textbook Question

Using cyclohexanone as the starting material, describe how each of the following compounds can be synthesized:

Textbook Question

Show how m-toluidine can be converted to the following compounds, using any necessary reagents.

(f)

Textbook Question

Using any necessary reagents, show how you would accomplish the following syntheses.