Textbook Question
Propose a mechanism for the hydrolysis of N,N-dimethylacetamide
(b) under acidic conditions.
1
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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 22
Propose a mechanism for the basic hydrolysis of benzonitrile to the benzoate ion and ammonia.
Verified step by step guidance1
Identify the functional group in benzonitrile: The nitrile group (-C≡N) is a triple bond between carbon and nitrogen. In basic hydrolysis, this group is converted into a carboxylate ion (-COO⁻) and ammonia (NH₃).
Recognize the role of the base: The hydroxide ion (OH⁻) acts as a nucleophile and attacks the electrophilic carbon in the nitrile group, breaking the triple bond and forming an intermediate imidate ion.
Describe the intermediate hydrolysis step: The imidate ion undergoes further reaction with water, leading to the formation of an amide intermediate (benzamide). This step involves proton transfer and rearrangement.
Explain the second nucleophilic attack: The hydroxide ion attacks the carbonyl carbon of the amide, leading to the cleavage of the C-N bond and the formation of a tetrahedral intermediate.
Conclude with the final products: The tetrahedral intermediate collapses, releasing ammonia (NH₃) and forming the benzoate ion (C₆H₅COO⁻) as the final products of the reaction.
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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 mechanism in organic chemistry where a nucleophile attacks an electrophile, resulting in the replacement of a leaving group. In the case of benzonitrile hydrolysis, water acts as a nucleophile, attacking the carbon atom of the nitrile group, leading to the formation of an intermediate that eventually yields benzoate and ammonia.
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Nucleophiles and Electrophiles can react in Substitution Reactions.
Hydrolysis of Nitriles
Hydrolysis of nitriles involves the reaction of a nitrile with water, typically under basic or acidic conditions, to convert it into a carboxylic acid and ammonia. In this process, the nitrile carbon is converted to a carboxylate ion, while the nitrogen is released as ammonia, highlighting the transformation of functional groups during the reaction.
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Reaction Mechanism
A reaction mechanism is a step-by-step description of the pathway taken during a chemical reaction, detailing the formation and breakdown of intermediates. Understanding the mechanism of benzonitrile hydrolysis is crucial, as it outlines the sequence of nucleophilic attack, intermediate formation, and final product generation, providing insight into the reaction's kinetics and thermodynamics.
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Related Practice
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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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In which step(s) of the hydride reduction of an ester does the compound undergo reduction? (Hint: Count the bonds to oxygen.)
1
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Textbook Question
Propose a mechanism for the reduction of octanoyl chloride by lithium aluminum hydride.
1
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Textbook Question
Propose a mechanism for the hydrolysis of N,N-dimethylacetamide
(a) under basic conditions.
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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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