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

Amine Alkylation

Organic Chemistry

26. Amines

Amine Alkylation

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6:29 minutes

Problem 17a

Textbook Question

Explain why the reaction of an alkyl halide with ammonia gives a low yield of primary amine.

Verified step by step guidance

Step 1: Understand the reaction mechanism. The reaction of an alkyl halide with ammonia involves nucleophilic substitution, where ammonia acts as a nucleophile and replaces the halide group in the alkyl halide.

Step 2: Recognize the issue of over-alkylation. Ammonia can react further with the primary amine product to form secondary, tertiary amines, and even quaternary ammonium salts. This leads to a low yield of the desired primary amine.

Step 3: Consider the competing reactions. The primary amine formed initially is also nucleophilic and can attack additional alkyl halide molecules, leading to the formation of secondary and tertiary amines.

Step 4: Explore alternative methods to improve yield. One such method is the use of alkyl azides, as shown in the image. The alkyl azide avoids over-alkylation and can be reduced to the primary amine using hydrogenation (H₂/Pd-C).

Step 5: Analyze the reaction shown in the image. The alkyl halide reacts with azide ion (N₃⁻) to form an alkyl azide, which is then reduced to the primary amine (CH₃CH₂CH₂NH₂) with the release of nitrogen gas (N₂). This method circumvents the issue of over-alkylation and provides a higher yield of the primary amine.

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Key Concepts

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

Alkyl Halides

Alkyl halides are organic compounds containing a carbon chain bonded to a halogen atom (F, Cl, Br, I). They are key substrates in nucleophilic substitution reactions, where the halogen is replaced by a nucleophile, such as ammonia. The structure and reactivity of alkyl halides influence the outcome of reactions, including the formation of amines.

Nucleophilic Substitution

Nucleophilic substitution is a fundamental reaction in organic chemistry where a nucleophile attacks an electrophilic carbon atom, displacing a leaving group. In the case of alkyl halides reacting with ammonia, the nucleophilic nitrogen in ammonia attacks the carbon bonded to the halogen, leading to the formation of an amine. However, steric hindrance and competing reactions can lead to low yields of the desired product.

Competing Reactions

In reactions involving alkyl halides and ammonia, competing reactions can significantly affect product yield. For instance, secondary and tertiary amines can form through further reactions of primary amines with alkyl halides, leading to a mixture of products. Additionally, elimination reactions may occur, further reducing the yield of the desired primary amine.

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