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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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 25b
Draw the most stable conformation of
b. 3-isopropyl-1,1-dimethylcyclohexane.
Verified step by step guidance1
Identify the structure of 3-isopropyl-1,1-dimethylcyclohexane. The cyclohexane ring is the base structure, with an isopropyl group at carbon 3 and two methyl groups at carbon 1.
Draw the cyclohexane ring in its chair conformation, which is the most stable conformation due to minimized steric strain.
Place the two methyl groups at carbon 1. Since they are on the same carbon, one will be axial and the other equatorial. To minimize steric hindrance, place the larger group (isopropyl) in the equatorial position.
Position the isopropyl group at carbon 3. To achieve the most stable conformation, place the isopropyl group in the equatorial position, as it is bulkier than a methyl group.
Verify the stability of the conformation by ensuring that the larger substituents (isopropyl and one of the methyl groups) are in equatorial positions, reducing 1,3-diaxial interactions and overall steric strain.
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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. In the chair form, carbon atoms are staggered, reducing repulsion between hydrogen atoms. Understanding these conformations is crucial for determining the most stable structure of substituted cyclohexanes.
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03:29
Understanding what a conformer is.
Axial and Equatorial Positions
In the chair conformation of cyclohexane, substituents can occupy axial or equatorial positions. Axial positions are perpendicular to the ring plane, while equatorial positions are parallel. Larger groups prefer equatorial positions to minimize steric hindrance, which is key to determining the most stable conformation of substituted cyclohexanes.
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04:02Equatorial Preference
Steric Hindrance
Steric hindrance occurs when atoms or groups are too close, causing repulsion and destabilizing the molecule. In cyclohexane derivatives, placing bulky groups in equatorial positions reduces steric hindrance, leading to a more stable conformation. Recognizing steric effects is essential for predicting the stability of different conformations.
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02:53Understanding steric effects.
Related Practice
Textbook Question
Draw the most stable conformation of
c. cis-1-tert-butyl-4-isopropylcyclohexane.
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Textbook Question
Draw the most stable conformation of
a. ethylcyclohexane.
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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
Draw a Newman projection, similar to Figure 3-25 down the C1—C6 bond in the equatorial conformation of methylcyclohexane. Show that the equatorial methyl group is also anti to C5. (Using your models will help.)
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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)
3
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