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.
(b) Repeat part (a) for the acid-catalyzed hydrolysis of this compound.
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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 14a
Propose a mechanism for the following ring-opening transesterification. Use the mechanism in Problem 21-13 as a model.
Verified step by step guidance1
Identify the reactants and products in the ring-opening transesterification reaction. Typically, this involves a cyclic ester (lactone) reacting with an alcohol to form a linear ester.
Recognize the key steps in a transesterification mechanism: nucleophilic attack, tetrahedral intermediate formation, and reformation of the carbonyl group with the departure of a leaving group.
Initiate the mechanism by having the alcohol (nucleophile) attack the carbonyl carbon of the lactone. This step forms a tetrahedral intermediate. Represent this step using the general structure of the lactone and alcohol.
Show the collapse of the tetrahedral intermediate. The original ester bond in the lactone breaks, leading to the formation of a linear ester and the release of the leaving group (typically an alkoxide or hydroxide).
Ensure that all charges and electron movements are accounted for in the mechanism. Use curved arrows to indicate the flow of electrons, and confirm that the final products are consistent with the reaction conditions and the reactants provided.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Transesterification
Transesterification is a chemical reaction where an ester is converted into another ester through the exchange of the alkoxy group. This process typically involves the nucleophilic attack of an alcohol on the carbonyl carbon of the ester, leading to the formation of a new ester and the release of the original alcohol. Understanding this mechanism is crucial for analyzing the ring-opening transesterification mentioned in the question.
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General Reaction
Mechanism of Ring-Opening Reactions
Ring-opening reactions involve the breaking of a cyclic structure to form a linear or open-chain product. In the context of transesterification, this often requires the presence of a nucleophile that attacks the electrophilic carbon in the ring, leading to the opening of the ring and subsequent formation of new bonds. Familiarity with these mechanisms is essential for proposing a detailed pathway for the reaction.
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Nucleophilic Attack
Nucleophilic attack is a fundamental concept in organic chemistry where a nucleophile, which is an electron-rich species, attacks an electrophile, an electron-deficient species. In the context of transesterification, the alcohol acts as a nucleophile, attacking the carbonyl carbon of the ester. Understanding this interaction is key to elucidating the mechanism of the ring-opening transesterification process.
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Related Practice
Textbook Question
When ethyl 4-hydroxybutyrate is heated in the presence of a trace of a basic catalyst (sodium acetate), one of the products is a lactone. Propose a mechanism for formation of this lactone.
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Textbook Question
Propose a mechanism for the acid-catalyzed hydrolysis of phenylalanine ethyl ester.
Textbook Question
Acid-catalyzed transesterification:
Complete the mechanism for this acid-catalyzed transesterification by drawing out all the individual steps. Draw the important resonance contributors for each resonance-stabilized intermediate.
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Textbook Question
1. Propose a mechanism for the acid-catalyzed reaction of salicylic acid with acetic anhydride.
2. Explain why a single drop of sulfuric acid dramatically increases the reaction rate.
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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.
(a) Draw a mechanism for the hydrolysis of this compound under basic conditions. Predict which of the products will contain the 18O label. Also predict whether the butan-2-ol product will be pure (R), pure (S), or racemized.
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