Textbook Question
Propose mechanisms for the following reactions.
(e)
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Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds
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
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Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 78a,b
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 78a,bChapter 22, Problem 78a,b
Write equations showing the expected products of the following enamine alkylation and acylation reactions. Then give the final products expected after hydrolysis of the iminium salts.
(a) pyrrolidine enamine of pentan-3-one + allyl chloride
(b) pyrrolidine enamine of acetophenone + butanoyl chloride
Verified step by step guidance1
Step 1: Understand the enamine reaction mechanism. Enamines are nucleophilic at the α-carbon due to resonance stabilization. They react with electrophiles such as alkyl halides (in alkylation) or acyl chlorides (in acylation) to form iminium salts.
Step 2: For part (a), identify the enamine structure. The pyrrolidine enamine of pentan-3-one is formed by the reaction of pyrrolidine with pentan-3-one. The enamine has a double bond between the α-carbon and the nitrogen, with the nitrogen bonded to the pyrrolidine ring.
Step 3: Perform the alkylation reaction for part (a). The nucleophilic α-carbon of the enamine attacks the electrophilic carbon of allyl chloride, displacing the chloride ion and forming a new C-C bond. This results in an iminium salt intermediate.
Step 4: For part (b), identify the enamine structure. The pyrrolidine enamine of acetophenone is formed by the reaction of pyrrolidine with acetophenone. The enamine has a double bond between the α-carbon and the nitrogen, with the nitrogen bonded to the pyrrolidine ring.
Step 5: Perform the acylation reaction for part (b). The nucleophilic α-carbon of the enamine attacks the electrophilic carbonyl carbon of butanoyl chloride, displacing the chloride ion and forming an iminium salt. Finally, hydrolyze the iminium salts from both reactions (a) and (b) with water to regenerate the corresponding ketones or aldehydes as the final products.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Enamines
Enamines are derivatives of imines formed by the reaction of secondary amines with carbonyl compounds. They contain a carbon-carbon double bond adjacent to a nitrogen atom, which makes them nucleophilic. This nucleophilicity allows enamines to react with electrophiles, such as alkyl halides or acyl chlorides, facilitating alkylation and acylation reactions.
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Enamine Mechanism
Iminium Salts
Iminium salts are positively charged intermediates formed during the reaction of enamines with electrophiles. When an enamine reacts with an electrophile, it forms an iminium salt, which can be hydrolyzed to yield the final product. Understanding the formation and hydrolysis of iminium salts is crucial for predicting the final products of the reactions in question.
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Hydrolysis
Hydrolysis is a chemical reaction involving the breakdown of a compound by water. In the context of iminium salts, hydrolysis leads to the regeneration of the original carbonyl compound and the corresponding amine. This step is essential for determining the final products after the alkylation or acylation of the enamine, as it reveals the transformation of the iminium salt back into stable products.
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Related Practice
Textbook Question
Write equations showing the expected products of the following enamine alkylation and acylation reactions. Then give the final products expected after hydrolysis of the iminium salts.
(d) piperidine enamine of cyclopentanone + methyl vinyl ketone
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Textbook Question
Write equations showing the expected products of the following enamine alkylation and acylation reactions. Then give the final products expected after hydrolysis of the iminium salts.
(c) piperidine enamine of cyclopentanone + methyl iodide
983
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Textbook Question
Propose mechanisms for the following reactions.
(d)
553
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Textbook Question
Propose mechanisms for the following reactions.
(c)
776
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Textbook Question
Show how you would accomplish the following multistep conversions. You may use any additional reagents you need.
(a)
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