Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

4. Alkanes and Cycloalkanes

Equatorial Preference

Organic Chemistry

4. Alkanes and Cycloalkanes

Equatorial Preference

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3:20 minutes

Problem 74d

Textbook Question

Draw the two chair conformers for each of the following and indicate which conformer is more stable:
d. cis-1,2-diethylcyclohexane

Verified step by step guidance

Step 1: Begin by understanding the structure of cyclohexane and its chair conformations. Cyclohexane can adopt two chair conformations, which are interconvertible through a ring flip. Each carbon atom in the chair conformation has two substituent positions: axial (pointing up or down, perpendicular to the ring) and equatorial (pointing outward, roughly parallel to the ring plane).

Step 2: Analyze the substituents in cis-1,2-diethylcyclohexane. The 'cis' designation means that both ethyl groups are on the same side of the ring. Assign the substituents to positions on adjacent carbons in the chair conformation, ensuring they are both either axial or equatorial to maintain the cis relationship.

Step 3: Draw the first chair conformer. Place one ethyl group in the axial position on carbon 1 and the other ethyl group in the axial position on carbon 2. Ensure the cis relationship is preserved by keeping both substituents on the same side of the ring.

Step 4: Draw the second chair conformer by performing a ring flip. In this conformer, the ethyl group on carbon 1 will move to the equatorial position, and the ethyl group on carbon 2 will also move to the equatorial position. Again, ensure the cis relationship is maintained.

Step 5: Compare the stability of the two conformers. Substituents in the equatorial position experience less steric hindrance compared to axial positions. Therefore, the conformer with both ethyl groups in equatorial positions is more stable due to reduced 1,3-diaxial interactions.

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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 a three-dimensional representation of cyclohexane that minimizes steric strain and torsional strain. In this conformation, the carbon atoms are arranged in a staggered manner, allowing for more stable interactions between substituents. Understanding chair conformations is crucial for analyzing the stability of cyclohexane derivatives, as different substituents can occupy axial or equatorial positions, affecting overall stability.

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 arrangement significantly influences the steric interactions between substituents, which in turn affects the stability of the conformers. For cis-1,2-diethylcyclohexane, both ethyl groups will be on the same side, impacting their positioning in the chair conformations.

Stability of Conformers

The stability of chair conformers is determined by the positioning of substituents in axial or equatorial orientations. Equatorial positions are generally more stable due to reduced steric hindrance and torsional strain compared to axial positions, where substituents can experience 1,3-diaxial interactions. When analyzing the stability of cis-1,2-diethylcyclohexane, it is essential to compare the steric effects of the ethyl groups in both chair conformers to determine which is more stable.

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Related Practice

Textbook Question

For each pair of conformations shown, choose which is most stable. If both are equally stable, then write 'no difference.' [If both conformations have the same number of axial substituents, choose the one with the smallest axial substituents.]

(g)

Textbook Question

For each structure shown, draw the two chair conformations and choose which is most stable. Be sure that your second chair is the flipped version of the first. [Make sure that wedged substituents are up in the chair, regardless of whether up is equatorial or axial.]

(e)

Textbook Question

(g)

Textbook Question

Draw the two chair conformers for each of the following and indicate which conformer is more stable:

b. trans-1-ethyl-2-methylcyclohexane

Textbook Question

Draw the more stable chair conformer of cis-1-ethyl-2-methylcyclohexane.

Textbook Question

Which compound is more stable: cis-1-ethyl-2-methylcyclohexane or trans-1-ethyl-2-methylcyclohexane?

Textbook Question

Which compound is more stable: cis-1-ethyl-2-methylcyclohexane or trans-1-ethyl-2-methylcyclohexane?

Textbook Question

Draw the most stable chair conformation for the following trisubstituted cyclohexane.

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Draw the two chair conformers for each of the following and indicate which conformer is more stable: d. cis-1,2-diethylcyclohexane

Key Concepts

Chair Conformation

Cis and Trans Isomerism

Stability of Conformers

Watch next

Draw the two chair conformers for each of the following and indicate which conformer is more stable:
d. cis-1,2-diethylcyclohexane