Textbook Question
a. Draw both chair conformations of cis-1,4-dimethylcyclohexane, and determine which conformer is more stable.
b. Repeat for the trans isomer.
c. Predict which isomer (cis or trans) is more stable.
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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 25c
Draw the most stable conformation of
c. cis-1-tert-butyl-4-isopropylcyclohexane.
Verified step by step guidance1
Identify the cyclohexane ring and understand that it can adopt different conformations, primarily chair conformations, which are the most stable due to minimized steric strain.
Recognize that the substituents on the cyclohexane ring are a tert-butyl group at position 1 and an isopropyl group at position 4. Since the compound is 'cis', both groups will be on the same side of the ring.
Draw the cyclohexane in a chair conformation. Place the tert-butyl group in an equatorial position at carbon 1 to minimize steric hindrance, as it is the larger group.
Since the compound is 'cis', the isopropyl group at carbon 4 should also be placed equatorially on the same side of the ring as the tert-butyl group. This ensures both groups are on the same side, maintaining the 'cis' configuration.
Verify the stability of the conformation by ensuring that both bulky groups (tert-butyl and isopropyl) are in equatorial positions, which reduces steric strain and makes the conformation more stable.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cyclohexane Conformations
Cyclohexane can adopt several conformations, with the chair conformation being the most stable due to minimized steric strain and torsional strain. Understanding how substituents interact in these conformations is crucial for determining stability.
Recommended video:
Guided course
03:29
Understanding what a conformer is.
Cis Configuration
In organic chemistry, 'cis' refers to the arrangement where two substituents are on the same side of a molecule. For cyclohexane derivatives, this affects how substituents are positioned in the chair conformation, influencing steric interactions and overall stability.
Recommended video:
Guided course
02:14The Electron Configuration
Steric Hindrance
Steric hindrance occurs when bulky groups in a molecule interfere with each other, affecting the molecule's stability. In cyclohexane, larger groups like tert-butyl and isopropyl prefer equatorial positions to minimize steric strain, impacting the most stable conformation.
Recommended video:
Guided course
02:53Understanding steric effects.
Related Practice
Textbook Question
Name the following compounds. Remember that two up bonds are cis; two down bonds are cis; one up bond and one down bond are trans.
(e)
(f)
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Textbook Question
Draw the most stable conformation of
a. ethylcyclohexane.
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Textbook Question
Draw the most stable conformation of
b. 3-isopropyl-1,1-dimethylcyclohexane.
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Textbook Question
Table 3-6 shows that the axial–equatorial energy difference for methyl, ethyl, and isopropyl groups increases gradually: 7.6, 7.9, and 8.8 kJ/mol (1.8, 1.9, and 2.1 kcal/mol). The tert-butyl group jumps to an energy difference of 23 kJ/mol (5.4 kcal/mol), over twice the value for the isopropyl group. Draw pictures of the axial conformations of isopropylcyclohexane and tert-butylcyclohexane, and explain why the tert-butyl substituent experiences such a large increase in axial energy over the isopropyl group.
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Textbook Question
Name the following compounds. Remember that two up bonds are cis; two down bonds are cis; one up bond and one down bond are trans.
(c)
(d)
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