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

Cis vs Trans Conformations

Organic Chemistry

4. Alkanes and Cycloalkanes

Cis vs Trans Conformations

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5:52 minutes

Problem 28

Textbook Question

Use your results from Problem 3-27 to complete the following table. Each entry shows the positions of two groups arranged as shown. For example, two groups that are trans on adjacent carbons (trans-1,2) must be both equatorial (e,e) or both axial (a,a).

Verified step by step guidance

Understand the concept of stereochemistry and conformational analysis, focusing on the terms 'axial' and 'equatorial' positions in cyclohexane rings.

Recall that in cyclohexane, substituents can be positioned either axially (parallel to the axis of the ring) or equatorially (around the equator of the ring). This affects the stability of the molecule.

Consider the stereochemical relationship between substituents on adjacent carbons. For trans-1,2 substituents, both groups must be in the same type of position (either both axial or both equatorial) to maintain the trans configuration.

Apply the same logic to other configurations such as cis-1,2, trans-1,3, and cis-1,3, considering how the positions (axial/equatorial) affect the stereochemistry and stability of the molecule.

Use your understanding of these principles to fill in the table, ensuring that each pair of substituents is correctly assigned to either axial or equatorial positions based on their stereochemical relationship.

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Key Concepts

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

Cis-Trans Isomerism

Cis-trans isomerism refers to the arrangement of substituents around a double bond or a ring structure. In cis isomers, substituents are on the same side, while in trans isomers, they are on opposite sides. This concept is crucial for understanding how the spatial arrangement affects the stability and properties of molecules, particularly in cyclohexane chair conformations.

Cyclohexane Chair Conformation

Cyclohexane can adopt a chair conformation, which is the most stable due to minimized steric strain. In this conformation, substituents can occupy axial or equatorial positions. Axial positions are perpendicular to the ring plane, while equatorial positions are parallel, affecting the molecule's stability and reactivity. Understanding this helps in predicting the preferred arrangement of groups in cis-trans isomers.

Axial and Equatorial Positions

In cyclohexane chair conformations, substituents can be axial (pointing up or down from the ring) or equatorial (extending outward from the ring plane). Equatorial positions are generally more stable due to less steric hindrance. Recognizing these positions is essential for determining the most stable configuration of substituents, especially in trans-1,2 arrangements where both groups must be either axial or equatorial.

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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.

(c)

Textbook Question

Is each of the following a cis isomer or a trans isomer?

Textbook Question

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

(b)

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)

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.

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)

Textbook Question

Which of the following represents a cis isomer?

Textbook Question

Name the following cycloalkanes using the IUPAC system of nomenclature.

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