Textbook Question
Use a Newman projection about the indicated bond to draw the most stable conformer for each compound.
a. 3-methylpentane about the C2―C3 bond
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Ch.3 - Structure and Stereochemistry of Alkanes
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 3, Problem 42c
In each pair of compounds, which compound has the higher boiling point? Explain your reasoning.
c. 2,2,5-trimethylhexane or nonane
Verified step by step guidance1
Step 1: Understand the concept of boiling point. Boiling point is the temperature at which a substance transitions from a liquid to a gas. It is influenced by intermolecular forces; stronger forces result in higher boiling points.
Step 2: Identify the types of intermolecular forces present in the compounds. Both 2,2,5-trimethylhexane and nonane are alkanes, which primarily exhibit van der Waals forces (London dispersion forces).
Step 3: Consider the molecular structure and size. Nonane (C₉H₂₀) is a straight-chain alkane, while 2,2,5-trimethylhexane (C₉H₂₀) is a branched alkane. Straight-chain alkanes generally have stronger dispersion forces due to greater surface area contact compared to branched alkanes.
Step 4: Compare the molecular weight and surface area. Both compounds have the same molecular formula, C₉H₂₀, indicating identical molecular weights. However, nonane's linear structure allows for more effective intermolecular interactions than the branched structure of 2,2,5-trimethylhexane.
Step 5: Conclude which compound has the higher boiling point. Based on the analysis, nonane, with its straight-chain structure, is expected to have a higher boiling point than 2,2,5-trimethylhexane due to stronger van der Waals forces.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Boiling Point
The boiling point of a compound is the temperature at which its vapor pressure equals the atmospheric pressure, causing it to transition from liquid to gas. It is influenced by molecular weight, intermolecular forces, and molecular structure. Stronger intermolecular forces, such as hydrogen bonding or van der Waals forces, typically result in higher boiling points.
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Intermolecular Forces
Intermolecular forces are the forces that hold molecules together, affecting physical properties like boiling points. In hydrocarbons, van der Waals forces (dispersion forces) are predominant. Larger molecules with greater surface area generally exhibit stronger van der Waals forces, leading to higher boiling points compared to smaller or more compact molecules.
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Molecular Structure and Branching
The structure of a molecule, including its branching, significantly impacts its boiling point. Linear molecules, like nonane, have more surface area for intermolecular interactions compared to branched molecules like 2,2,5-trimethylhexane. Branching reduces surface contact between molecules, weakening van der Waals forces and typically resulting in lower boiling points.
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Related Practice
Textbook Question
There are eight different five-carbon alkyl groups.
c. In each case, label the degree of substitution (primary, secondary, or tertiary) of the head carbon atom bonded to the main chain.
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Textbook Question
The following names are all incorrect or incomplete, but they represent real structures. Draw each structure and name it correctly.
e. 2-cyclohexylbutane
f. 2,3-diethylcyclopentane
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Textbook Question
In each pair of compounds, which compound has the higher boiling point? Explain your reasoning.
b. nonane or 2-methylheptane
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Textbook Question
In each pair of compounds, which compound has the higher boiling point? Explain your reasoning.
a. octane or 2,2,3-trimethylpentane
Textbook Question
There are eight different five-carbon alkyl groups.
a. Draw them.
b. Give them systematic names.
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