Textbook Question
Draw the two chair conformers for each of the following and indicate which conformer is more stable:
d. cis-1,2-diethylcyclohexane
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Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure
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. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and StructureProblem 74e
Bruice 8th EditionCh. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and StructureProblem 74eChapter 4, Problem 74e
Draw the two chair conformers for each of the following and indicate which conformer is more stable:
e. cis-1-ethyl-3-isopropylcyclohexane
Verified step by step guidance1
Step 1: Begin by understanding the structure of cyclohexane and its chair conformations. Cyclohexane can adopt two chair conformations, which are interconvertible through a ring flip. Each carbon atom in the chair conformation has two substituent positions: axial (pointing up or down, perpendicular to the ring) and equatorial (pointing outward, roughly parallel to the ring).
Step 2: Identify the substituents on the cyclohexane ring. In this case, the molecule is cis-1-ethyl-3-isopropylcyclohexane. 'Cis' means that both substituents (ethyl and isopropyl groups) are on the same side of the ring. Assign the substituents to specific carbons: the ethyl group is on carbon 1, and the isopropyl group is on carbon 3.
Step 3: Draw the first chair conformer. Place the ethyl group on carbon 1 in the axial position and the isopropyl group on carbon 3 in the axial position as well, ensuring they are both on the same side of the ring to satisfy the 'cis' configuration.
Step 4: Draw the second chair conformer by performing a ring flip. In the ring flip, axial substituents become equatorial, and equatorial substituents become axial. Place the ethyl group on carbon 1 in the equatorial position and the isopropyl group on carbon 3 in the equatorial position, maintaining the 'cis' configuration.
Step 5: Compare the stability of the two conformers. Generally, bulky groups prefer the equatorial position due to reduced steric hindrance. Since both the ethyl and isopropyl groups are relatively bulky, the conformer with both substituents in equatorial positions is more stable.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Chair Conformation
Chair conformation is a three-dimensional representation of cyclohexane that minimizes steric strain and torsional strain. In this conformation, the carbon atoms are arranged in a staggered manner, allowing for more stable interactions between substituents. Understanding chair conformations is crucial for analyzing the stability of cyclohexane derivatives, as substituents can occupy axial or equatorial positions, influencing overall stability.
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Understanding what a conformer is.
Axial vs. Equatorial Positions
In chair conformations, substituents can occupy either axial or equatorial positions. Axial substituents are oriented parallel to the axis of the ring, while equatorial substituents extend outward from the ring. Generally, equatorial positions are more stable for larger groups due to reduced steric hindrance and 1,3-diaxial interactions, which are unfavorable when bulky groups are in axial positions.
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Cis and Trans Isomerism
Cis and trans isomerism refers to the spatial arrangement of substituents around a cyclohexane ring. In cis isomers, substituents are on the same side of the ring, while in trans isomers, they are on opposite sides. This arrangement affects the stability of the conformers, as cis substituents may lead to increased steric strain when both are in axial positions, making it essential to evaluate their positions when determining the more stable conformer.
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Related Practice
Textbook Question
Draw the two chair conformers for each of the following and indicate which conformer is more stable:
c. trans-1-ethyl-2-isopropylcyclohexane
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Textbook Question
Draw the two chair conformers for each of the following and indicate which conformer is more stable:
f. cis-1-ethyl-4-isopropylcyclohexane
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Textbook Question
Draw the two chair conformers for each of the following and indicate which conformer is more stable:
b. trans-1-ethyl-2-methylcyclohexane
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Textbook Question
Draw a potential energy diagram for rotation about the C¬C bond of 1,2-dichloroethane through 360°, starting with the least stable conformer. The anti conformer is 1.2 kcal/mol more stable than a gauche conformer. A gauche conformer has two energy barriers, 5.2 kcal/mol and 9.3 kcal/mol.
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Textbook Question
Why are lower molecular weight alcohols more soluble in water than higher molecular weight alcohols?
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