Textbook Question
Propose a mechanism for the hydrolysis of N,N-dimethylacetamide
(b) under acidic conditions.
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Ch. 21 - Carboxylic Acid Derivatives
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 21, Problem 20a
Propose a mechanism for the hydrolysis of N,N-dimethylacetamide
(a) under basic conditions.
Verified step by step guidance1
Step 1: Identify the functional groups in N,N-dimethylacetamide. The molecule contains an amide functional group, which consists of a carbonyl group (C=O) directly bonded to a nitrogen atom (N). The nitrogen is substituted with two ethyl groups.
Step 2: Understand the reaction conditions. Under basic conditions, hydrolysis involves the attack of hydroxide ions (OH⁻) on the carbonyl carbon of the amide group. This is facilitated by the electrophilic nature of the carbonyl carbon.
Step 3: Initiate the mechanism. The hydroxide ion (OH⁻) acts as a nucleophile and attacks the electrophilic carbonyl carbon, forming a tetrahedral intermediate. This intermediate has the oxygen atom bearing a negative charge and the nitrogen atom still attached.
Step 4: Break the C-N bond. The tetrahedral intermediate undergoes rearrangement, leading to the cleavage of the bond between the carbonyl carbon and the nitrogen atom. This results in the formation of a carboxylate ion (RCOO⁻) and a free amine (N,N-dimethylethylamine).
Step 5: Finalize the products. Under basic conditions, the carboxylate ion remains deprotonated due to the presence of excess hydroxide ions, and the amine remains neutral. The final products are the carboxylate ion and the amine.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hydrolysis Mechanism
Hydrolysis is a chemical reaction involving the breaking of a bond in a molecule using water. In the case of N,N-dimethylacetamide, the hydrolysis mechanism under basic conditions typically involves nucleophilic attack by hydroxide ions (OH-) on the carbonyl carbon, leading to the formation of a tetrahedral intermediate. This intermediate can then collapse, resulting in the formation of the corresponding carboxylic acid and amine.
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Hydrolysis of Nucleosides Concept 1
Nucleophilic Attack
Nucleophilic attack is a fundamental concept in organic chemistry where a nucleophile, which is an electron-rich species, attacks an electron-deficient site, usually a carbon atom in a carbonyl group. In the hydrolysis of N,N-dimethylacetamide, the hydroxide ion acts as the nucleophile, attacking the carbonyl carbon, which is susceptible to nucleophilic attack due to the partial positive charge created by the oxygen's electronegativity.
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08:27Nucleophilic Addition
Basic Conditions
Basic conditions refer to an environment where the pH is greater than 7, typically involving the presence of hydroxide ions (OH-). In the hydrolysis of N,N-dimethylacetamide under basic conditions, the hydroxide ions not only facilitate the nucleophilic attack but also help in deprotonating the amine product, leading to the formation of a more stable product. Understanding the role of the base is crucial for predicting the reaction pathway and products.
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06:21Understanding the difference between basicity and nucleophilicity.
Related Practice
Textbook Question
Show how the following ketones might be synthesized from the indicated acids, using any necessary reagents.
(a) propiophenone from propionic acid (using Friedel–Crafts acylation)
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Textbook Question
Propose a mechanism for the base-promoted hydrolysis of γ-butyrolactone:
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Textbook Question
Draw the important resonance contributors for both resonance-stabilized cations (in brackets) in the mechanism for acid-catalyzed hydrolysis of an amide.
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Textbook Question
The mechanism for acidic hydrolysis of a nitrile resembles the basic hydrolysis, except that the nitrile is first protonated, activating it toward attack by a weak nucleophile (water). Under acidic conditions, the proton transfer (tautomerism) involves protonation on nitrogen followed by deprotonation on oxygen. Propose a mechanism for the acid-catalyzed hydrolysis of benzonitrile to benzamide.
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Textbook Question
Propose a mechanism for the basic hydrolysis of benzonitrile to the benzoate ion and ammonia.
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