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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6:18 minutes

Problem 30b

Textbook Question

Draw the most stable conformation of
b. trans-1-tert-butyl-2-methylcyclohexane.

Verified step by step guidance

Identify the cyclohexane ring and the substituents: In this problem, we have a cyclohexane ring with a tert-butyl group and a methyl group attached at the 1 and 2 positions, respectively.

Understand the 'trans' configuration: The 'trans' configuration means that the two substituents are on opposite sides of the cyclohexane ring. One will be axial and the other equatorial.

Draw the chair conformation of cyclohexane: Cyclohexane can adopt a chair conformation, which is the most stable due to minimized steric strain. Draw the chair structure with alternating axial and equatorial positions.

Place the tert-butyl group: The tert-butyl group is bulky, so it should be placed in the equatorial position to minimize steric hindrance. Choose one carbon (C1) and place the tert-butyl group equatorially.

Place the methyl group: Since the configuration is 'trans', the methyl group should be placed on the opposite side of the ring from the tert-butyl group. If the tert-butyl is equatorial, the methyl group should be axial on the adjacent carbon (C2).

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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 the chair conformation is crucial for determining the stability of substituted cyclohexanes, as it allows for the analysis of axial and equatorial positions of substituents.

Axial and Equatorial Positions

In the chair conformation of cyclohexane, substituents can occupy axial or equatorial positions. Axial positions are parallel to the axis of the ring, while equatorial positions extend outward. Equatorial positions are generally more stable for bulky groups due to reduced steric hindrance, which is essential for determining the most stable conformation of substituted cyclohexanes.

Trans Configuration

The trans configuration in cyclohexane refers to substituents being on opposite sides of the ring. For trans-1-tert-butyl-2-methylcyclohexane, this means the tert-butyl and methyl groups are positioned across from each other. Understanding this configuration helps in correctly placing substituents in the chair conformation to achieve the most stable arrangement.

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Related Practice

Textbook Question

Draw the two chair conformations of each of the following substituted cyclohexanes. In each case, label the more stable conformation.

a. cis-1-ethyl-2-methylcyclohexane

b. trans-1,2-diethylcyclohexane

Textbook Question

The most stable form of the common sugar glucose contains a six-membered ring in the chair conformation with all the substituents equatorial. Draw this most stable conformation of glucose.

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.

Textbook Question

Draw the most stable conformation of

c. trans-1-tert-butyl-3-(1,1-dimethylpropyl)cyclohexane.

Textbook Question

Draw the most stable conformation of

a. cis-1-tert-butyl-3-ethylcyclohexane.

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.

Textbook Question

Draw the two chair conformations of each compound, and label the substituents as axial and equatorial. In each case, determine which conformation is more stable.

e. cis-1-ethyl-4-methylcyclohexane

f. trans-1-ethyl-4-methylcyclohexane

Textbook Question

Draw the two chair conformations of each compound, and label the substituents as axial and equatorial. In each case, determine which conformation is more stable.

a. cis-1-ethyl-2-isopropylcyclohexane

b. trans-1-ethyl-2-isopropylcyclohexane

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Draw the most stable conformation of b. trans-1-tert-butyl-2-methylcyclohexane.

Key Concepts

Cyclohexane Conformations

Axial and Equatorial Positions

Trans Configuration

Watch next

Draw the most stable conformation of
b. trans-1-tert-butyl-2-methylcyclohexane.