Textbook Question
Show how you would accomplish the following synthetic conversions.
(c) pentanoic acid → pentan-1-amine
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Ch. 19 - Amines
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 19, Problem 30b
Show how you would accomplish the following synthetic conversions.
(b) 1-bromo-2-phenylethane → 3-phenylpropan-1-amine
Verified step by step guidance1
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.
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Nucleophiles and Electrophiles can react in Substitution Reactions.
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.
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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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Related Practice
Textbook Question
Show how Gabriel syntheses are used to prepare the following amines.
(a) benzylamine
(b) hexan-1-amine
(c) γ-aminobutyric acid
1399
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Textbook Question
Show how you would accomplish the following synthetic conversions.
(d) pentanoic acid → hexan-1-amine
1109
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Textbook Question
Addition of one equivalent of ammonia to 1-bromoheptane gives a mixture of heptan-1-amine, some dialkylamine, some trialkylamine, and even some tetraalkylammonium bromide.
(a) Give a mechanism to show how this reaction takes place, as far as the dialkylamine.
(b) How would you modify the procedure to get an acceptable yield of heptan-1-amine?
980
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Textbook Question
Show how you would accomplish the following synthetic conversions.
(e) (R)-2-bromobutane → (S)-butan-2-amine
1162
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Textbook Question
Show how you would accomplish the following synthetic conversions.
(a) benzyl bromide → benzylamine
830
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