Textbook Question
Which compound is more stable: cis-1-ethyl-2-methylcyclohexane or trans-1-ethyl-2-methylcyclohexane?
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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 50a
Bruice 8th EditionCh. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and StructureProblem 50aChapter 4, Problem 50a
Draw the more stable chair conformer of cis-1-ethyl-2-methylcyclohexane.
Verified step by step guidance1
Understand the structure of cyclohexane and its chair conformations. Cyclohexane can adopt a chair conformation where substituents can occupy either axial (parallel to the ring's axis) or equatorial (perpendicular to the ring's axis) positions. Equatorial positions are generally more stable due to reduced steric hindrance.
Identify the substituents on the cyclohexane ring. In this case, the molecule is cis-1-ethyl-2-methylcyclohexane, meaning the ethyl group and the methyl group are on the same side of the ring (both pointing either up or down).
Assign the substituents to the correct positions on the chair conformation. Start by placing the ethyl group at carbon-1 and the methyl group at carbon-2. Since the molecule is cis, both substituents must be on the same side of the ring (either both axial or both equatorial).
Evaluate the stability of the two possible chair conformations. Place the larger substituent (ethyl group) in the equatorial position to minimize steric hindrance. This means the methyl group will also need to be equatorial in the same conformation to maintain the cis relationship.
Draw the final chair conformation with the ethyl group and methyl group both in equatorial positions. This is the more stable chair conformer of cis-1-ethyl-2-methylcyclohexane.
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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 the most stable three-dimensional arrangement of cyclohexane rings, minimizing steric strain and torsional strain. In this conformation, the carbon atoms are arranged in a staggered manner, allowing for optimal bond angles and reducing the repulsion between adjacent substituents. Understanding chair conformations is crucial for predicting the stability of substituted cyclohexanes.
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Understanding what a conformer is.
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 distinction affects the steric interactions and overall stability of the molecule, making it essential to identify the correct isomer when drawing conformers.
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Substituent Positioning
The positioning of substituents in chair conformations significantly influences the stability of cyclohexane derivatives. Substituents can occupy axial (up or down) or equatorial (outward) positions, with equatorial positions generally being more stable due to reduced steric hindrance. For cis-1-ethyl-2-methylcyclohexane, placing the larger substituent in the equatorial position is key to drawing the most stable conformer.
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Related Practice
Textbook Question
Is each of the following a cis isomer or a trans isomer?
a,
b.
c.
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Textbook Question
For each of the following disubstituted cyclohexanes, indicate whether the substituents in the two chair conformers are both equatorial in one chair conformer and both axial in the other or one equatorial and one axial in each of the chair conformers:
a. cis-1,2-
b. trans-1,2-
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Textbook Question
Which has a higher percentage of the diequatorial-substituted conformer compared with the diaxialsubstituted conformer: trans-1,4-dimethylcyclohexane or cis-1-tert-butyl-3-methylcyclohexane?
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Textbook Question
For each of the following disubstituted cyclohexanes, indicate whether the substituents in the two chair conformers are both equatorial in one chair conformer and both axial in the other or one equatorial and one axial in each of the chair conformers:
c. cis-1,3-
d. trans-1,3-
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Textbook Question
Is each of the following a cis isomer or a trans isomer?
d.
e.
f.
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