Textbook Question
a. When a carboxylic acid is dissolved in isotopically labeled water (H2O18) and an acid catalyst is added, the label is incorporated into both oxygens of the acid. Propose a mechanism to account for this.
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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 78
Bruice 8th EditionCh. 15 - Reactions of Carboxylic Acids and Carboxylic Acid DerivativesProblem 78Chapter 16, Problem 78
a. A student did not obtain any ester when he added 2,4,6-trimethylbenzoic acid to an acidic solution of ethanol. Why? (HINT: Build models.)
b. Would he have encountered the same problem if he had tried to synthesize the methyl ester of 4-methylbenzoic acid in the same way?
Verified step by step guidance1
Step 1: Understand the reaction mechanism for esterification. Esterification is typically carried out by reacting a carboxylic acid with an alcohol in the presence of an acid catalyst. The reaction proceeds via a nucleophilic attack of the alcohol on the carbonyl carbon of the carboxylic acid, followed by the elimination of water.
Step 2: Analyze the structure of 2,4,6-trimethylbenzoic acid. This compound has three bulky methyl groups attached to the benzene ring at positions 2, 4, and 6. These groups create significant steric hindrance around the carboxylic acid group, making it difficult for the ethanol molecule to approach and react with the carbonyl carbon.
Step 3: Consider the role of steric hindrance in the reaction. The steric hindrance caused by the bulky methyl groups prevents the nucleophilic ethanol from effectively attacking the carbonyl carbon of the carboxylic acid. As a result, the esterification reaction does not proceed, and no ester is formed.
Step 4: Compare this to 4-methylbenzoic acid. In this compound, there is only one methyl group at the 4-position of the benzene ring. This single methyl group does not create significant steric hindrance around the carboxylic acid group, allowing the ethanol to approach and react with the carbonyl carbon more easily.
Step 5: Conclude that the student would not encounter the same problem with 4-methylbenzoic acid. The reduced steric hindrance in this case would allow the esterification reaction to proceed, resulting in the formation of the methyl ester.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Esterification Reaction
Esterification is a chemical reaction between an alcohol and a carboxylic acid, resulting in the formation of an ester and water. This process typically requires an acid catalyst to proceed efficiently. In the case of 2,4,6-trimethylbenzoic acid and ethanol, steric hindrance from the bulky methyl groups can impede the reaction, preventing ester formation.
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Steric Hindrance
Steric hindrance refers to the prevention of reactions at a particular location within a molecule due to the size of substituent groups. In the context of 2,4,6-trimethylbenzoic acid, the three methyl groups create a crowded environment around the carboxylic acid functional group, making it difficult for the ethanol to approach and react, thus inhibiting ester formation.
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Comparison of Reactivity
When comparing the reactivity of different carboxylic acids, the structure and substituents play a crucial role. The methyl ester of 4-methylbenzoic acid may have less steric hindrance than 2,4,6-trimethylbenzoic acid, potentially allowing for successful esterification with ethanol. Understanding how substituents affect reactivity is essential for predicting the outcomes of organic reactions.
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Related Practice
Textbook Question
An aqueous solution of a primary or secondary amine reacts with an acyl chloride to form an amide as the major product. However, if the amine is tertiary, an amide is not formed. What product is formed? Explain.
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Textbook Question
a. When a carboxylic acid is dissolved in isotopically labeled water (H2O18) and an acid catalyst is added, the label is incorporated into both oxygens of the acid. Propose a mechanism to account for this.
c. If an ester is dissolved in isotopically labeled water (H2O18) and an acid catalyst is added, where will the label reside in the product?
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Textbook Question
Identify the major and minor products of the following reaction:
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Textbook Question
When a compound with molecular formula C11H14O2 undergoes acid-catalyzed hydrolysis, one of the products that is isolated gives the following 1H NMR spectrum. Identify the compound.
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Textbook Question
Cardura, a drug used to treat hypertension, is synthesized as shown here.
a. Identify the intermediate (A) and show the mechanism for its formation.
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