Textbook Question
Use the four compounds shown below to answer the following questions:
b. Why is o-fluorobenzoic acid the weakest of the ortho-halo-substituted benzoic acids?
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Ch. 18 - Reactions of Benzene and Substituted Benzenes
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
Chapter 19, Problem 66a
Use the four compounds shown below to answer the following questions:
a. Why are the ortho-halo-substituted benzoic acids stronger acids than benzoic acid?
Verified step by step guidance1
Step 1: Begin by analyzing the structure of benzoic acid (compound A). Benzoic acid consists of a benzene ring attached to a carboxylic acid group (-COOH). The acidity of benzoic acid is influenced by the electron-withdrawing or electron-donating effects of substituents on the benzene ring.
Step 2: Examine the ortho-substituted nitrobenzoic acid (compound B). The nitro group (-NO₂) is an electron-withdrawing group due to its strong inductive and resonance effects. When positioned ortho to the carboxylic acid group, it stabilizes the conjugate base (benzoate ion) by delocalizing the negative charge through resonance.
Step 3: Consider the proximity of the nitro group in compound B. The ortho position allows for additional stabilization via intramolecular hydrogen bonding between the nitro group and the carboxylic acid group. This further increases the acidity of the compound compared to unsubstituted benzoic acid.
Step 4: Compare compound B (ortho-nitrobenzoic acid) with compound C (meta-nitrobenzoic acid) and compound D (para-nitrobenzoic acid). While the nitro group in the meta and para positions also exerts an electron-withdrawing effect, the ortho position provides the strongest stabilization due to the combination of inductive effects, resonance effects, and intramolecular hydrogen bonding.
Step 5: Conclude that ortho-halo-substituted benzoic acids (or ortho-nitrobenzoic acids in this case) are stronger acids than benzoic acid because the substituent at the ortho position enhances the stabilization of the conjugate base through resonance and intramolecular interactions, making it easier for the compound to donate a proton.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acidity and Acid Strength
Acidity refers to the ability of a compound to donate protons (H+ ions) in solution. The strength of an acid is determined by its dissociation constant (Ka), which indicates how completely it ionizes in water. Stronger acids have higher Ka values, meaning they release protons more readily. In the context of benzoic acid and its derivatives, substituents can influence acidity by stabilizing or destabilizing the conjugate base formed after deprotonation.
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03:09
The 3 factors that determine the strength of inductive effects.
Inductive Effect
The inductive effect is the transmission of charge through a chain of atoms in a molecule due to the electronegativity of nearby atoms. Electron-withdrawing groups, such as nitro (-NO2), can stabilize the negative charge on the conjugate base of an acid, thereby increasing its acidity. In ortho-substituted benzoic acids, the proximity of the nitro group enhances this effect, making these acids stronger than benzoic acid itself.
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Resonance Stabilization
Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, allowing for the delocalization of electrons. In the case of nitro-substituted benzoic acids, the resonance structures can distribute the negative charge of the conjugate base over several atoms, further stabilizing it. This stabilization is particularly pronounced in ortho-substituted compounds, where the nitro group can participate in resonance with the carboxylate group, enhancing acidity.
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Related Practice
Textbook Question
b. Rank the same esters from most reactive to least reactive in the second slow step of a nucleophilic acyl substitution reaction (collapse of the tetrahedral intermediate).
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Textbook Question
a. Rank the following esters from most reactive to least reactive in the first slow step of a nucleophilic acyl substitution reaction (formation of the tetrahedral intermediate):
Textbook Question
Show how the following compounds can be synthesized from benzene:
g. p-dideuteriobenzene
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Textbook Question
Show how the following compounds can be synthesized from benzene:
h. p-nitro-N-methylaniline
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Textbook Question
Show how the following compounds can be synthesized from benzene:
a. N,N,N-trimethylanilinium iodide
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