Textbook Question
Explain why the pKa of p-nitrophenol is 7.14, whereas the pKa of m-nitrophenol is 8.39.
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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 Benzene
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. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of BenzeneProblem 20d,e,f
Bruice 8th EditionCh. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of BenzeneProblem 20d,e,fChapter 9, Problem 20d,e,f
For each of the following substituents, indicate whether it withdraws electrons inductively, donates electrons by hyperconjugation, withdraws electrons by resonance, or donates electrons by resonance.
d. NHCH3
e. OCH3
f. +N(CH3)3
Verified step by step guidance1
Step 1: Understand the four electronic effects mentioned in the problem: (1) Inductive electron withdrawal occurs when a substituent pulls electron density through sigma bonds due to its electronegativity. (2) Hyperconjugation involves the donation of electron density through overlap of sigma bonds with an adjacent empty or partially filled orbital. (3) Resonance electron withdrawal happens when a substituent withdraws electron density through delocalization of electrons via pi bonds. (4) Resonance electron donation occurs when a substituent donates electron density through delocalization of lone pairs or pi electrons into the conjugated system.
Step 2: Analyze the substituent in part (d). Determine if the substituent has electronegative atoms or groups that can withdraw electrons inductively, lone pairs that can participate in resonance donation, or pi systems that can withdraw electrons by resonance.
Step 3: Analyze the substituent in part (e). Follow the same process as in Step 2, identifying whether the substituent exhibits inductive withdrawal, hyperconjugation donation, resonance withdrawal, or resonance donation based on its structure and electronic properties.
Step 4: Analyze the substituent in part (f). Again, evaluate the substituent's ability to withdraw or donate electrons through inductive effects, hyperconjugation, or resonance mechanisms. Pay attention to the presence of electronegative atoms, lone pairs, or conjugated systems.
Step 5: Summarize the findings for each substituent (d, e, f) based on the analysis. Clearly indicate which electronic effect(s) each substituent exhibits, ensuring the reasoning aligns with the substituent's structure and electronic characteristics.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Inductive Effect
The inductive effect refers to the permanent polarization of a bond due to the electronegativity difference between atoms. Electronegative atoms or groups can withdraw electron density from adjacent atoms, leading to a decrease in electron density in the molecule. This effect diminishes with distance and is crucial for understanding how substituents influence the reactivity and stability of organic compounds.
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Resonance Effect
The resonance effect involves the delocalization of electrons across multiple atoms in a molecule, which can stabilize the structure. Electron-donating groups can provide electron density through resonance, while electron-withdrawing groups can pull electron density away. Understanding resonance is essential for predicting the behavior of substituents in reactions and their impact on molecular stability.
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Hyperconjugation
Hyperconjugation is a stabilizing interaction that occurs when electron density from a filled orbital (usually a sigma bond) interacts with an adjacent empty orbital (like a pi bond or a carbocation). This effect can lead to increased stability in certain molecular structures, particularly in carbocations, and is important for understanding how alkyl groups can donate electron density to positively charged centers.
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Related Practice
Textbook Question
Which member of each pair is the stronger base?
a. ethylamine or aniline
b. ethylamine or ethoxide ion
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Textbook Question
Which acid in each of the following pairs is stronger?
e.
f.
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Textbook Question
Which acid in each of the following pairs is stronger?
c.
d.
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Textbook Question
Which member of each pair is the stronger base?
c. phenolate ion or ethoxide ion
d. phenolate ion or acetate ion
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Textbook Question
For each of the following substituents, indicate whether it withdraws electrons inductively, donates electrons by hyperconjugation, withdraws electrons by resonance, or donates electrons by resonance.
a. Br
b. CH2CH3
c.
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