Textbook Question
Which ester hydrolyzes more rapidly? a. methyl acetate or phenyl acetate?
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Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
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Bruice 8th EditionCh. 15 - Reactions of Carboxylic Acids and Carboxylic Acid DerivativesProblem 21c,d
Bruice 8th EditionCh. 15 - Reactions of Carboxylic Acids and Carboxylic Acid DerivativesProblem 21c,dChapter 16, Problem 21c,d
In the mechanism for the acid-catalyzed hydrolysis of an ester,
c. what species is HB+ most likely to be in the hydrolysis reaction?
d. what species is HB+ most likely to be in the reverse reaction?
Verified step by step guidance1
Step 1: Understand the context of the problem. The acid-catalyzed hydrolysis of an ester involves breaking the ester bond in the presence of an acid catalyst, typically resulting in the formation of a carboxylic acid and an alcohol. The acid catalyst donates a proton (H⁺) to facilitate the reaction.
Step 2: Identify the role of HB⁺ in the hydrolysis reaction. HB⁺ represents the conjugate acid of the base (B) present in the reaction. In the hydrolysis reaction, HB⁺ is most likely the protonated form of the solvent or a species that can donate a proton to stabilize intermediates.
Step 3: Analyze the forward reaction (hydrolysis). In the forward reaction, water (H₂O) is typically the nucleophile that attacks the carbonyl carbon of the ester. The acid catalyst (H⁺) protonates the carbonyl oxygen to make the carbonyl carbon more electrophilic. HB⁺ is most likely H₃O⁺ (hydronium ion), which is the protonated form of water.
Step 4: Analyze the reverse reaction (esterification). In the reverse reaction, the carboxylic acid and alcohol combine to reform the ester. The acid catalyst (H⁺) protonates the hydroxyl group of the carboxylic acid to make it a better leaving group. HB⁺ in this case is also most likely H₃O⁺, as the reaction occurs in an acidic environment.
Step 5: Conclude that in both the forward (hydrolysis) and reverse (esterification) reactions, HB⁺ is most likely H₃O⁺, as it is the conjugate acid of water and plays a key role in the acid-catalyzed mechanism.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Catalyzed Hydrolysis
Acid-catalyzed hydrolysis is a reaction where an ester reacts with water in the presence of an acid catalyst, typically a proton donor like HCl or H2SO4. The acid increases the electrophilicity of the carbonyl carbon in the ester, facilitating the nucleophilic attack by water. This process results in the formation of an alcohol and a carboxylic acid.
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Acid Catalyzed
Protonation and HB+ Species
In organic reactions, HB+ represents a protonated species, often a conjugate acid formed when a base accepts a proton. In the context of acid-catalyzed hydrolysis, HB+ is likely to be the protonated form of the alcohol or water, which stabilizes the transition state and promotes the reaction. Understanding the role of HB+ is crucial for predicting the direction and products of the reaction.
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Reversibility of Reactions
Many organic reactions, including hydrolysis, are reversible. In the reverse reaction, the products (alcohol and carboxylic acid) can recombine to form the original ester, especially under certain conditions. The species HB+ in the reverse reaction is typically the protonated form of the carboxylic acid, which can facilitate the reformation of the ester by donating a proton to the alcohol.
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Related Practice
Textbook Question
Using the mechanism for the acid-catalyzed hydrolysis of an ester as your guide, write the mechanism—showing all the curved arrows—for the acid-catalyzed reaction of acetic acid and methanol to form methyl acetate. Use HB+ and :B to represent the proton-donating and proton-removing species, respectively.
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Textbook Question
Write a mechanism for each of the following reactions:
b. the aminolysis of phenyl formate, using methylamine.
Textbook Question
What products are formed from the acid-catalyzed hydrolysis of the following esters?
a.
b.
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Textbook Question
Show the mechanism for the acid-catalyzed formation of 23c starting with the product obtained from its hydrolysis.
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Textbook Question
Which ester hydrolyzes more rapidly? b. phenyl acetate or benzyl acetate?
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