Textbook Question
Propose a mechanism to show the individual alkylations that form this quaternary ammonium salt.
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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 16
Show how you would use direct alkylation to synthesize the following compounds.
(a) benzyltrimethylammonium iodide
(b) pentan-1-amine
(c) benzylamine
Verified step by step guidance1
Step 1: Understand the concept of direct alkylation. Direct alkylation involves the reaction of an amine (or ammonia) with an alkyl halide to form a substituted amine. This reaction proceeds via an SN2 mechanism, where the nucleophilic amine attacks the electrophilic carbon of the alkyl halide, displacing the halide ion.
Step 2: For (a) benzyltrimethylammonium iodide, start with trimethylamine as the nucleophile. React trimethylamine with benzyl iodide (C6H5CH2I). The nucleophilic nitrogen in trimethylamine will attack the benzyl carbon, displacing the iodide ion and forming benzyltrimethylammonium iodide.
Step 3: For (b) pentan-1-amine, begin with ammonia (NH3) as the nucleophile. React ammonia with 1-bromopentane (CH3(CH2)4Br). The nucleophilic nitrogen in ammonia will attack the primary carbon of 1-bromopentane, displacing the bromide ion and forming pentan-1-amine.
Step 4: For (c) benzylamine, use ammonia (NH3) as the nucleophile again. React ammonia with benzyl bromide (C6H5CH2Br). The nucleophilic nitrogen in ammonia will attack the benzyl carbon, displacing the bromide ion and forming benzylamine.
Step 5: Ensure that the reaction conditions are controlled to avoid over-alkylation. For primary amines like pentan-1-amine and benzylamine, use an excess of ammonia to minimize the formation of secondary and tertiary amines. For quaternary ammonium salts like benzyltrimethylammonium iodide, use a stoichiometric amount of the alkyl halide to achieve the desired product.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Direct Alkylation
Direct alkylation is a method used in organic synthesis to introduce an alkyl group into a molecule. This process typically involves the reaction of an alkyl halide with a nucleophile, such as an amine or an alkoxide. The choice of alkyl halide and the reaction conditions can significantly influence the yield and selectivity of the desired product.
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Directed Condensations
Quaternary Ammonium Salts
Benzyltrimethylammonium iodide is a quaternary ammonium salt formed by the alkylation of a tertiary amine. These salts are characterized by a positively charged nitrogen atom bonded to four carbon-containing groups. They are often used as phase transfer catalysts in organic reactions due to their ability to solubilize ionic compounds in organic solvents.
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Amine Synthesis
The synthesis of amines, such as pentan-1-amine and benzylamine, can be achieved through direct alkylation of ammonia or primary amines. This process involves the nucleophilic attack of the amine on an alkyl halide, leading to the formation of the corresponding amine. The choice of alkyl halide and the reaction conditions are crucial for achieving the desired amine product.
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Related Practice
Textbook Question
(a) Propose a mechanism for the reaction of 2-bromopyridine with sodium amide to give 2-aminopyridine.
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Textbook Question
Show how you would use the same sulfonyl chloride as used in the sulfanilamide synthesis to make sulfathiazole and sulfapyridine.
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Textbook Question
(b) When 3-bromopyridine is used in this reaction, stronger reaction conditions are required and a mixture of 3-aminopyridine and 4-aminopyridine results. Propose a mechanism to explain this curious result.
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Textbook Question
Give the products expected from the following reactions.
(a) acetyl chloride + ethylamine
(b)
(c)
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Textbook Question
What would happen in the synthesis of sulfanilamide if the amino group were not protected as an amide in the chlorosulfonation step?
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