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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6:27 minutes

Problem 47b

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

Verified step by step guidance

Identify the starting material (benzaldehyde) and the target product (benzylamine). Benzaldehyde is an aromatic aldehyde, and benzylamine is a primary amine. This suggests that reductive amination is a suitable method for this transformation.

In reductive amination, the carbonyl group of the aldehyde reacts with an amine to form an imine intermediate. In this case, ammonia (NH₃) will be used as the amine source to form the imine.

Write the reaction for the formation of the imine: Benzaldehyde reacts with ammonia (NH₃) under acidic or neutral conditions to form an imine (C₆H₅CH=NH). This step involves nucleophilic attack of ammonia on the carbonyl carbon, followed by dehydration to form the imine.

The imine intermediate is then reduced to the corresponding amine (benzylamine) using a reducing agent. Common reducing agents for this step include sodium cyanoborohydride (NaBH₃CN) or hydrogen gas (H₂) with a metal catalyst like palladium (Pd) or nickel (Ni).

Combine the steps into the overall reaction: Benzaldehyde reacts with ammonia to form an imine intermediate, which is subsequently reduced to benzylamine using a suitable reducing agent. This completes the synthesis of benzylamine from benzaldehyde via reductive amination.

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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 two-step process involving the reaction of a carbonyl compound, such as an aldehyde or ketone, with an amine to form an imine or enamine, followed by reduction to yield an amine. In the case of benzaldehyde, it reacts with ammonia or an amine to form an intermediate imine, which is then reduced to benzylamine using a reducing agent like sodium cyanoborohydride.

Reduction of Amides

The reduction of amides involves converting an amide functional group into an amine by adding hydrogen or a reducing agent. This process typically requires stronger reducing agents, such as lithium aluminum hydride (LiAlH4), which can effectively reduce the carbonyl carbon of the amide to yield the corresponding amine. While this method is not directly applicable to the synthesis of benzylamine from benzaldehyde, it is a fundamental concept in amine synthesis.

Mechanism of Carbonyl Reactions

Understanding the mechanism of carbonyl reactions is crucial for predicting the outcomes of reactions involving carbonyl compounds. In the case of benzaldehyde, the nucleophilic attack by the amine on the electrophilic carbon of the carbonyl group leads to the formation of a tetrahedral intermediate, which can then collapse to form the imine. This mechanistic insight is essential for grasping how reductive amination can be employed to synthesize benzylamine.

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Textbook Question

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

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

Propose mechanisms for the following reactions.

(a)

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)

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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

Key Concepts

Reductive Amination

Reduction of Amides

Mechanism of Carbonyl Reactions

Watch next

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