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 24a
In which step(s) of the hydride reduction of an ester does the compound undergo reduction? (Hint: Count the bonds to oxygen.)
Verified step by step guidance1
Step 1: Understand the hydride reduction of an ester. This reaction typically involves the use of a reducing agent like lithium aluminum hydride (LiAlH₄) to convert the ester into an alcohol. The process occurs in multiple steps.
Step 2: Recall the definition of reduction in organic chemistry. Reduction involves a decrease in the number of bonds to oxygen or an increase in the number of bonds to hydrogen in a molecule.
Step 3: Analyze the first step of the reaction. The hydride ion (H⁻) from the reducing agent attacks the carbonyl carbon of the ester, breaking the π bond of the carbonyl group and forming a tetrahedral intermediate. At this stage, the carbonyl carbon gains a bond to hydrogen, which is a reduction step.
Step 4: Examine the second step of the reaction. The tetrahedral intermediate collapses, expelling the leaving group (usually an alkoxide ion, R'O⁻) and forming an aldehyde. This step does not involve a change in the number of bonds to oxygen for the carbonyl carbon, so it is not a reduction step.
Step 5: Consider the final step. The aldehyde undergoes a second hydride attack, forming a new tetrahedral intermediate that eventually becomes a primary alcohol. In this step, the carbonyl carbon again gains a bond to hydrogen, making it another reduction step.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hydride Reduction
Hydride reduction is a chemical reaction where a hydride ion (H-) is used to reduce a carbonyl compound, such as an ester, to an alcohol. This process typically involves the transfer of a hydride from a reducing agent, like lithium aluminum hydride (LiAlH4) or sodium borohydride (NaBH4), to the carbonyl carbon, resulting in the formation of an alcohol and the conversion of the carbonyl group.
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Ester Structure
Esters are organic compounds characterized by the functional group -COOR, where R is an alkyl or aryl group. In the context of reduction, understanding the structure of esters is crucial, as they contain a carbonyl group (C=O) and an alkoxy group (–O–R). The reduction process involves the conversion of the carbonyl group to an alcohol, which requires counting the bonds to oxygen to determine the extent of reduction.
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Bond Counting in Reduction
In organic chemistry, bond counting is a method used to assess the degree of reduction or oxidation of a compound. For esters undergoing hydride reduction, it is essential to count the bonds to oxygen before and after the reaction. The reduction of the carbonyl group (C=O) to an alcohol (C–OH) involves a change from one double bond to one single bond and the addition of a hydrogen atom, indicating a reduction in oxidation state.
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Related Practice
Textbook Question
Draw a mechanism for the acidic hydrolysis of the magnesium salt shown below to acetophenone.
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Textbook Question
Draw a mechanism for the reaction of propanoyl chloride with 2 moles of phenylmagnesium bromide.
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Textbook Question
Propose a mechanism for the reduction of octanoyl chloride by lithium aluminum hydride.
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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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