Textbook Question
Rank each set of compounds in order of increasing basicity.
(b) aniline, p-methylaniline, p-nitroaniline
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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 6d
Rank each set of compounds in order of increasing basicity.
(d) pyrrole, imidazole, 3-nitropyrrole
Verified step by step guidance1
Step 1: Understand the concept of basicity. Basicity refers to the ability of a compound to donate a lone pair of electrons to accept a proton (H⁺). In organic chemistry, the basicity of nitrogen-containing heterocycles is influenced by factors such as electron density, resonance, and the presence of electron-withdrawing or electron-donating groups.
Step 2: Analyze pyrrole (structure i). Pyrrole has a nitrogen atom with a lone pair of electrons that is delocalized into the aromatic ring system. This delocalization reduces the availability of the lone pair for protonation, making pyrrole less basic.
Step 3: Analyze imidazole (structure ii). Imidazole contains two nitrogen atoms, one of which has a lone pair that is not involved in aromatic delocalization. This lone pair is readily available for protonation, making imidazole more basic than pyrrole.
Step 4: Analyze 3-nitropyrrole (structure iii). The nitro group (-NO₂) is a strong electron-withdrawing group that decreases the electron density on the nitrogen atom in the pyrrole ring. This further reduces the basicity of 3-nitropyrrole compared to pyrrole.
Step 5: Rank the compounds in order of increasing basicity. Based on the analysis, 3-nitropyrrole is the least basic due to the electron-withdrawing nitro group, followed by pyrrole with delocalized lone pair electrons, and imidazole is the most basic due to the availability of a lone pair for protonation.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Basicity in Organic Chemistry
Basicity refers to the ability of a compound to accept protons (H+) in a chemical reaction. In organic chemistry, basicity is influenced by the availability of lone pairs on nitrogen atoms, which can bond with protons. Compounds with more electron-donating groups tend to be more basic, while those with electron-withdrawing groups are less basic.
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Aromaticity and Basicity
Aromatic compounds, such as pyrrole and imidazole, exhibit unique stability due to resonance and delocalization of electrons. This aromatic character can affect basicity; for instance, in pyrrole, the nitrogen's lone pair is involved in the aromatic system, making it less available for protonation compared to imidazole, where the nitrogen's lone pair is more accessible.
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06:21Understanding the difference between basicity and nucleophilicity.
Electron-Withdrawing and Electron-Donating Groups
Electron-withdrawing groups (EWGs), like nitro groups (-NO2), decrease basicity by stabilizing the positive charge that forms upon protonation, making it less favorable. Conversely, electron-donating groups (EDGs) enhance basicity by increasing electron density on the nitrogen atom, facilitating protonation. Understanding these effects is crucial for ranking the basicity of the given compounds.
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Related Practice
Textbook Question
The proton and 13C NMR spectra of a compound of formula C4H11N are shown here. Determine the structure of this amine, and give peak assignments for all of the protons in the structure.
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Textbook Question
Rank each set of compounds in order of increasing basicity.
(c) aniline, pyrrole, pyridine, piperidine
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Textbook Question
Propose a mechanism for nitration of pyridine at the 4-position, and show why this orientation is not observed.
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Textbook Question
Propose a mechanism for the sulfonation of pyridine, and point out why sulfonation occurs at the 3-position.
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Textbook Question
Rank each set of compounds in order of increasing boiling points.
(a) triethylamine, di-n-propylamine, n-propyl ether
(b) ethanol, dimethylamine, dimethyl ether
(c) diethylamine, diisopropylamine, trimethylamine
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