Textbook Question
Within each structure, rank the indicated nitrogens by increasing basicity.
(a)
(b)
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Ch. 19 - Amines
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 19, Problem 33d
Rank the amines in each set in order of increasing basicity.
(d) 
Verified step by step guidance1
Step 1: Analyze the chemical structures provided. The three amines are aniline derivatives, each with a substituent on the benzene ring: (a) aniline (NH₂ group attached to benzene), (b) methyl-substituted aniline (CH₃ group attached to benzene), and (c) nitro-substituted aniline (NO₂ group attached to benzene).
Step 2: Understand the effect of substituents on the basicity of the amine group. Substituents can either donate or withdraw electron density from the benzene ring, which affects the availability of the lone pair on the nitrogen atom for protonation.
Step 3: Evaluate the electron-donating or electron-withdrawing nature of each substituent. The methyl group (CH₃) is an electron-donating group via hyperconjugation and inductive effects, increasing the electron density on the nitrogen atom and enhancing basicity. The nitro group (NO₂) is a strong electron-withdrawing group due to resonance and inductive effects, decreasing the electron density on the nitrogen atom and reducing basicity.
Step 4: Rank the amines based on their substituents' effects. The unsubstituted aniline (NH₂ group only) has intermediate basicity. The methyl-substituted aniline is more basic due to the electron-donating effect of the CH₃ group. The nitro-substituted aniline is the least basic due to the electron-withdrawing effect of the NO₂ group.
Step 5: Final ranking in order of increasing basicity: Nitro-substituted aniline < Unsubstituted aniline < Methyl-substituted aniline.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Basicity of Amines
Basicity in amines refers to their ability to accept protons (H+) in a chemical reaction. This property is influenced by the availability of the lone pair of electrons on the nitrogen atom, which can bond with protons. Factors such as steric hindrance and the presence of electron-donating or withdrawing groups can significantly affect the basicity of different amines.
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07:12
Reductive Amination
Inductive Effect
The inductive effect describes how the presence of electronegative atoms or groups near the amine can influence its basicity. Electron-withdrawing groups decrease basicity by stabilizing the lone pair on nitrogen, making it less available for protonation. Conversely, electron-donating groups enhance basicity by increasing electron density on nitrogen, facilitating proton acceptance.
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01:47Understanding the Inductive Effect.
Steric Hindrance
Steric hindrance refers to the repulsion between atoms due to their physical size, which can impede the approach of protons to the nitrogen atom in amines. In bulky amines, steric hindrance can reduce basicity as the nitrogen's lone pair becomes less accessible for bonding with protons. Understanding steric effects is crucial for ranking amines based on their basicity.
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02:53Understanding steric effects.
Related Practice
Textbook Question
Rank the amines in each set in order of increasing basicity.
(e)
2
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Textbook Question
Rank the amines in each set in order of increasing basicity.
(a)
1
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Textbook Question
For each compound,
(1) classify the nitrogen-containing functional groups.
(2) provide an acceptable name.
(g)
(h)
1
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Textbook Question
Within each structure, rank the indicated nitrogens by increasing basicity.
(c)
5
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Textbook Question
Rank the amines in each set in order of increasing basicity.
(c)
1
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