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Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
All textbooksMullins 1st EditionCh. 3 - Alkanes and Cycloalkanes: Properties and Conformational AnalysisProblem 40b
Chapter 2, Problem 40b

Given the following chair conformations, draw each in its planar form as if you were viewing it from above.
(b) Chair conformation diagram showing numbered carbon atoms and hydrogen for cis and trans isomer comparison.

Verified step by step guidance
1
Step 1: Understand the chair conformation. A chair conformation is a 3D representation of cyclohexane, where the carbon atoms alternate between being slightly above and below the plane. This minimizes steric strain and torsional strain.
Step 2: Identify the axial and equatorial positions. In a chair conformation, axial substituents point straight up or down (parallel to the vertical axis), while equatorial substituents extend outward (roughly perpendicular to the vertical axis). Locate these positions for each substituent on the given chair conformation.
Step 3: Translate the chair conformation into a planar form. To do this, draw a hexagon to represent the cyclohexane ring in a flat, top-down view. Place the substituents in their respective positions based on whether they are axial or equatorial in the chair conformation.
Step 4: Ensure correct stereochemistry. When drawing the planar form, use wedge bonds (solid triangles) to indicate substituents coming out of the plane toward the viewer, and dashed bonds (dotted lines) to indicate substituents going behind the plane.
Step 5: Double-check your drawing. Verify that the positions of the substituents in the planar form match the original chair conformation, maintaining the correct stereochemical relationships and avoiding errors in bond placement.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Chair Conformation

The chair conformation is a three-dimensional representation of cyclohexane that minimizes steric strain and torsional strain. It features alternating axial and equatorial bonds, allowing for more stable arrangements of substituents. Understanding this conformation is crucial for visualizing how substituents affect the molecule's overall stability and reactivity.
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Planar Representation

Planar representation refers to the two-dimensional depiction of a molecule, which simplifies the visualization of its structure. When converting a chair conformation to a planar form, it is essential to accurately represent the bond angles and distances to maintain the integrity of the molecular geometry. This representation helps in understanding the spatial arrangement of atoms and substituents.
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Axial and Equatorial Positions

In the chair conformation of cyclohexane, substituents can occupy either axial or equatorial positions. Axial substituents are oriented perpendicular to the plane of the ring, while equatorial substituents are oriented parallel to the plane. The choice of position significantly influences steric interactions and the overall stability of the molecule, making it a key factor in conformational analysis.
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Related Practice
Textbook Question

Given the following chair conformations, draw each in its planar form as if you were viewing it from above.

(d)

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Textbook Question

Name the following cycloalkanes using the IUPAC system of nomenclature, being sure to indicate whether they are cis or trans.

(b)

1018
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Textbook Question

Draw two chair conformations of the molecules below. Indicate which is most stable.

(a)

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Textbook Question

Draw two different chair conformations for each of the following molecules. Make sure that your drawings clearly show the cis–trans stereochemistry.

(c)

939
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Textbook Question

Given the following chair conformations, draw each in its planar form as if you were viewing it from above.

(c)

1509
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Textbook Question

Rank the following compounds in order of their total heat of combustion. These compounds are constitutional isomers, each with a molecular formula of C6H12.

252
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