Textbook Question
Propose mechanisms for the following reactions.
(e)
3
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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 78d
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 78dChapter 22, Problem 78d
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
Verified step by step guidance1
Step 1: Recognize the enamine structure. The piperidine enamine of cyclopentanone consists of a cyclopentanone ring with a double bond between the alpha-carbon and the nitrogen of the piperidine group. This enamine acts as a nucleophile in the reaction.
Step 2: Identify the electrophile. Methyl vinyl ketone (CH3-CH=CH-COCH3) is an alpha, beta-unsaturated ketone, which can undergo a Michael addition reaction with the enamine. The beta-carbon of the methyl vinyl ketone is the electrophilic site.
Step 3: Perform the Michael addition. The nucleophilic alpha-carbon of the enamine attacks the beta-carbon of the methyl vinyl ketone, forming a new carbon-carbon bond. This results in the formation of an intermediate iminium salt.
Step 4: Hydrolyze the iminium salt. The iminium salt formed in the previous step undergoes hydrolysis in the presence of water and an acid catalyst. This regenerates the original ketone group and removes the piperidine group, yielding the final product.
Step 5: Write the final product. The final product is a 1,5-diketone, where the cyclopentanone ring is now connected to the methyl vinyl ketone via a new carbon-carbon bond. Ensure the structure reflects the correct connectivity and functional groups.
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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 carbonyl compounds formed by the reaction of an aldehyde or ketone with a secondary amine. They contain a C=C bond adjacent to a nitrogen atom, which makes them nucleophilic and reactive towards electrophiles. This property allows enamines to participate in alkylation and acylation reactions, where they can form new carbon-carbon or carbon-heteroatom bonds.
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Enamine Mechanism
Iminium Salts
Iminium salts are positively charged intermediates formed when an enamine reacts with an electrophile, such as an alkyl halide or acyl chloride. The nitrogen atom in the enamine forms a bond with the electrophile, resulting in a structure that contains a double bond between carbon and nitrogen. Hydrolysis of these iminium salts typically leads to the regeneration of the carbonyl compound and the corresponding amine.
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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 results in the cleavage of the C=N bond, leading to the formation of a carbonyl compound and an amine. This reaction is crucial for completing the transformation of the initial enamine and allows for the recovery of the original carbonyl compound after alkylation or acylation.
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Related Practice
Textbook Question
Many of the condensations we have studied are reversible. The reverse reactions are often given the prefix retro-, the Latin word meaning “backward.” Propose mechanisms to account for the following reactions.
(b)
5
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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
1
views
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.
(a) pyrrolidine enamine of pentan-3-one + allyl chloride
(b) pyrrolidine enamine of acetophenone + butanoyl chloride
Textbook Question
Many of the condensations we have studied are reversible. The reverse reactions are often given the prefix retro-, the Latin word meaning “backward.” Propose mechanisms to account for the following reactions.
(a)
1
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Textbook Question
Show how you would accomplish the following multistep conversions. You may use any additional reagents you need.
(a)
3
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