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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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 18
Propose a mechanism for the base-promoted hydrolysis of γ-butyrolactone:
Verified step by step guidance1
Identify the structure of γ-butyrolactone, which is a cyclic ester (lactone) with a four-membered ring. The hydrolysis reaction involves breaking the ester bond to form a carboxylate and an alcohol group.
Recognize that the reaction is base-promoted, meaning a hydroxide ion (OH⁻) will act as the nucleophile. The hydroxide ion will attack the carbonyl carbon of the ester group in γ-butyrolactone, initiating the mechanism.
In the first step of the mechanism, the hydroxide ion performs a nucleophilic attack on the carbonyl carbon of the ester group. This forms a tetrahedral intermediate, where the carbonyl oxygen becomes negatively charged.
Next, the tetrahedral intermediate collapses, leading to the cleavage of the C-O bond in the lactone ring. This results in the formation of a carboxylate ion and an alcohol group.
Finally, confirm the products of the reaction: the carboxylate ion remains deprotonated under basic conditions, and the alcohol group is formed from the hydrolysis of the ester bond. The overall reaction converts γ-butyrolactone into a hydroxycarboxylate compound.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Lactone Structure and Reactivity
γ-Butyrolactone is a cyclic ester known as a lactone, formed from the condensation of a hydroxy acid. Its structure includes a five-membered ring containing an ester functional group, which makes it susceptible to nucleophilic attack. Understanding the reactivity of lactones is crucial for proposing a hydrolysis mechanism, as the ring strain and electronic properties influence how they interact with nucleophiles and bases.
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05:19
Lactones and Lactams
Base-Promoted Hydrolysis
Base-promoted hydrolysis involves the reaction of a lactone with a strong base, which facilitates the opening of the lactone ring. The base deprotonates a water molecule, generating a hydroxide ion that acts as a nucleophile. This nucleophile attacks the carbonyl carbon of the lactone, leading to the formation of a tetrahedral intermediate, which ultimately results in the formation of a carboxylic acid and an alcohol.
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04:04Base-Promoted Mechanism
Mechanistic Steps in Nucleophilic Substitution
The mechanism of nucleophilic substitution in the hydrolysis of γ-butyrolactone can be broken down into distinct steps: nucleophilic attack, formation of a tetrahedral intermediate, and collapse of this intermediate to yield the final products. Each step involves specific interactions between the nucleophile, the substrate, and the solvent, which are essential for understanding how the reaction proceeds and the factors that influence its rate and outcome.
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Related Practice
Textbook Question
Explain why we speak of acidic hydrolysis of an ester as acid-catalyzed, but of basic hydrolysis as base-promoted.
Textbook Question
Suppose we have some optically pure (R)-2-butyl acetate that has been 'labeled' with the heavy 18O isotope at one oxygen atom as shown.
(c) Explain how you would prove experimentally where the 18O label appears in the products. (18O is not radioactive.)
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Textbook Question
Soap manufacturers always use base to hydrolyze fats, and never acid. Suggest two reasons that basic hydrolysis is preferred.
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
Propose a mechanism for the hydrolysis of N,N-dimethylacetamide
(a) under basic conditions.
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