Textbook Question
Draw 1,2,3,4,5,6-hexamethylcyclohexane with all the methyl groups
a. in axial positions.
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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 23
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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Verified step by step guidance1
Step 1: Understand the problem. You are tasked with drawing a Newman projection down the C1-C6 bond in the equatorial conformation of methylcyclohexane. The goal is to show that the equatorial methyl group is anti to C5.
Step 2: Recall the chair conformation of cyclohexane. In the equatorial conformation, substituents are positioned outward from the ring, parallel to the plane of the ring. The axial positions alternate up and down, while the equatorial positions alternate slightly outward.
Step 3: Visualize the C1-C6 bond. In the chair conformation, C1 is at the front and C6 is at the back. To draw the Newman projection, imagine looking directly down the C1-C6 bond axis.
Step 4: Place the substituents in the Newman projection. At C1 (front carbon), the equatorial methyl group (CH3) will be positioned anti to the hydrogen on C5. At C6 (back carbon), the substituents will include hydrogens and the rest of the cyclohexane ring.
Step 5: Confirm the anti relationship. In the Newman projection, the equatorial methyl group at C1 will be directly opposite (anti) to the hydrogen on C5, as shown in the diagram. This anti relationship is due to the spatial arrangement in the chair conformation.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Newman Projections
Newman projections are a way to visualize the conformation of a molecule by looking straight down a bond connecting two carbon atoms. This representation helps in understanding steric interactions and torsional strain between substituents attached to the carbons. In the case of methylcyclohexane, drawing the Newman projection along the C1—C6 bond allows for a clear view of the spatial arrangement of the methyl group and other substituents.
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00:34
Introduction to Drawing Newman Projections
Equatorial vs. Axial Positions
In cyclohexane derivatives, substituents can occupy either equatorial or axial positions. The equatorial position is generally more stable as it minimizes steric hindrance with other axial substituents. In methylcyclohexane, the equatorial conformation allows the methyl group to be positioned away from the ring, reducing steric strain and making it easier to analyze its interactions with other groups, such as the C5 carbon.
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04:02Equatorial Preference
Anti Conformation
The term 'anti' refers to a specific spatial arrangement where two substituents are positioned 180 degrees apart in a Newman projection. In the context of methylcyclohexane, showing that the equatorial methyl group is anti to the C5 carbon means that these two groups are aligned in such a way that they are directly opposite each other, which is a favorable arrangement that minimizes steric interactions.
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03:19The Anti-Coplanar Requirement
Related Practice
Textbook Question
Draw 1,2,3,4,5,6-hexamethylcyclohexane with all the methyl groups
b. in equatorial positions.
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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
The cyclohexane chair shown in Figure 3-22 has the headrest to the right and the footrest to the left. Draw a cyclohexane chair with its axial and equatorial bonds, showing the headrest to the left and the footrest to the right.
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