Textbook Question
Predict which member of each pair is more soluble in water. Explain your prediction.
(e)
(f)
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Ch. 2 - Acids and Bases; Functional Groups
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 2, Problem 34c
N-Methylpyrrolidine has a boiling point of 81 °C, and piperidine has a boiling point of 106 °C.
c. N,N-Dimethylformamide has a boiling point of 150 °C, and N-methylacetamide has a boiling point of 206 °C, for a difference of 56 °C. Explain why these two nitrogen-containing isomers have a much larger boiling point difference than the two amine isomers. Also explain why these two amides have higher boiling points than any of the other four compounds shown (two amines, an ether, and an alcohol).
Verified step by step guidance1
Identify the functional groups present in each compound. N-Methylpyrrolidine and piperidine are amines, while N,N-Dimethylformamide and N-methylacetamide are amides.
Understand the intermolecular forces at play. Amines primarily engage in hydrogen bonding and dipole-dipole interactions, while amides can form stronger hydrogen bonds due to the presence of both a carbonyl group and an amine group.
Compare the boiling points of the amines and amides. The larger boiling point difference between the amides (56 °C) compared to the amines (25 °C) can be attributed to the stronger hydrogen bonding in amides, which involves both the carbonyl oxygen and the nitrogen hydrogen.
Explain why amides have higher boiling points than the other compounds. Amides have stronger hydrogen bonding capabilities than ethers and alcohols due to the presence of both a carbonyl group and an amine group, which allows for more extensive hydrogen bonding networks.
Conclude that the presence of the carbonyl group in amides significantly enhances their ability to engage in hydrogen bonding, leading to higher boiling points compared to amines, ethers, and alcohols.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hydrogen Bonding
Hydrogen bonding is a strong type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like nitrogen or oxygen. This interaction significantly increases boiling points due to the additional energy required to break these bonds. Amides, such as N-methylacetamide, can form hydrogen bonds due to the presence of both nitrogen and oxygen, leading to higher boiling points compared to amines, which primarily rely on nitrogen.
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The definition of hydrogenation.
Polarity and Molecular Structure
Polarity refers to the distribution of electrical charge over the atoms in a molecule. Molecules with polar bonds, like amides, have higher boiling points because the polar nature leads to stronger intermolecular forces. The molecular structure of N,N-dimethylformamide and N-methylacetamide includes a carbonyl group, which increases polarity and intermolecular attractions, resulting in higher boiling points compared to less polar amines.
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2:04Molecular Polarity
Intermolecular Forces
Intermolecular forces, including hydrogen bonding, dipole-dipole interactions, and van der Waals forces, determine the boiling points of compounds. Amides exhibit stronger intermolecular forces due to their ability to form hydrogen bonds and their polar nature, leading to higher boiling points. In contrast, amines primarily rely on weaker dipole-dipole interactions, resulting in lower boiling points compared to amides.
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Related Practice
Textbook Question
Diethyl ether and butan-1-ol are isomers, and they have similar solubilities in water. Their boiling points are very different, however. Explain why these two compounds have similar solubility properties but dramatically different boiling points.
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Textbook Question
Predict which compound in each pair has the higher boiling point. Explain your prediction.
(a) CH3CH2OCH3 or CH3CH(OH)CH3
(b) CH3CH2CH2CH3 or CH3CH2CH2CH2CH3
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Textbook Question
Predict which compound in each pair has the higher boiling point. Explain your prediction.
(e)
(f)
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Textbook Question
Predict which compound in each pair has the higher boiling point. Explain your prediction.
(c) CH3CH2CH2CH2CH3 or (CH3)2CH2CH2CH3
(d) CH3CH2CH2CH2CH3 or CH3CH2CH2CH2CH2Cl
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Textbook Question
N-Methylpyrrolidine has a boiling point of 81 °C, and piperidine has a boiling point of 106 °C.
b. Tetrahydropyran has a boiling point of 88 °C, and cyclopentanol has a boiling point of 141 °C. These two isomers have a boiling point difference of 53 °C. Explain why the two oxygen-containing isomers have a much larger boiling point difference than the two amine isomers.
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