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

Amines by Reduction

Organic Chemistry

26. Amines

Amines by Reduction

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3:50 minutes

Problem 30b

Textbook Question

Show how you would accomplish the following synthetic conversions.
(b) 1-bromo-2-phenylethane → 3-phenylpropan-1-amine

Verified step by step guidance

Step 1: Recognize that the starting material, 1-bromo-2-phenylethane, contains a bromine atom that can act as a leaving group. The target molecule, 3-phenylpropan-1-amine, contains an amine group (-NH2) at the terminal position. This suggests a nucleophilic substitution reaction followed by chain elongation.

Step 2: Perform a nucleophilic substitution reaction using cyanide ion (CN⁻) as the nucleophile. Treat 1-bromo-2-phenylethane with potassium cyanide (KCN) in an appropriate solvent like DMSO. This will replace the bromine atom with a nitrile group (-C≡N), forming 2-phenylacetonitrile.

Step 3: Reduce the nitrile group (-C≡N) in 2-phenylacetonitrile to a primary amine (-CH2-NH2). Use a reducing agent such as lithium aluminum hydride (LiAlH4) in anhydrous ether to achieve this transformation, yielding 3-phenylpropan-1-amine.

Step 4: Ensure proper workup after each reaction step. For the reduction step, carefully quench the reaction with water or dilute acid to neutralize excess LiAlH4 and isolate the amine product.

Step 5: Purify the final product, 3-phenylpropan-1-amine, using techniques such as distillation or recrystallization, depending on the physical properties of the compound.

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Key Concepts

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

Nucleophilic Substitution

Nucleophilic substitution is a fundamental reaction in organic chemistry where a nucleophile replaces a leaving group in a molecule. In this case, the bromine atom in 1-bromo-2-phenylethane acts as a leaving group, allowing the nucleophile (an amine) to attach to the carbon atom. Understanding the mechanisms of nucleophilic substitution, such as SN1 and SN2, is crucial for predicting the outcome of the reaction.

Amine Synthesis

Amine synthesis involves the formation of amines, which are organic compounds derived from ammonia by replacing one or more hydrogen atoms with alkyl or aryl groups. In the conversion from 1-bromo-2-phenylethane to 3-phenylpropan-1-amine, the introduction of an amine group is essential. Familiarity with various methods of amine synthesis, including reductive amination and nucleophilic substitution, is important for successful conversions.

Rearrangement Reactions

Rearrangement reactions involve the structural reorganization of a molecule, often leading to the formation of more stable or reactive products. In this conversion, the initial carbon skeleton of 1-bromo-2-phenylethane must be rearranged to form 3-phenylpropan-1-amine. Understanding how and why certain rearrangements occur, including the stability of intermediates, is key to predicting the products of synthetic pathways.

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