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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1:48 minutes

Problem 21

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.

Verified step by step guidance

Step 1: Understand the cyclohexane chair conformation. Cyclohexane adopts a chair conformation to minimize steric strain and torsional strain. In this conformation, the carbon atoms alternate between being slightly above and below the plane of the ring, creating a 'headrest' and 'footrest' appearance.

Step 2: Identify the axial and equatorial positions. In the chair conformation, each carbon atom has one axial bond (pointing straight up or down, perpendicular to the plane of the ring) and one equatorial bond (pointing outward, roughly parallel to the plane of the ring). These positions alternate around the ring.

Step 3: Reverse the orientation of the chair conformation. To draw the chair with the headrest to the left and the footrest to the right, flip the structure horizontally. This involves swapping the positions of the carbons while maintaining the alternating axial and equatorial bonds.

Step 4: Assign axial and equatorial bonds correctly. After flipping the chair, ensure that the axial bonds still alternate up and down around the ring, and the equatorial bonds remain roughly parallel to the plane of the ring. Use dashed and solid lines to distinguish between axial and equatorial bonds.

Step 5: Label the carbons and verify the structure. Number the carbons in the flipped chair conformation (1 through 6) to match the original numbering system. Double-check that the headrest is now on the left and the footrest is on the right, and that the axial and equatorial bonds are correctly positioned.

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Key Concepts

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

Cyclohexane Chair Conformation

The cyclohexane chair conformation is a three-dimensional structure that minimizes steric strain in cyclohexane rings. In this conformation, the carbon atoms are arranged in a staggered manner, allowing for more stable interactions between substituents. The chair form is the most stable conformation of cyclohexane due to its ability to avoid eclipsing interactions.

Axial and Equatorial Bonds

In the chair conformation of cyclohexane, substituents can occupy two types of positions: axial and equatorial. Axial bonds are oriented vertically, alternating up and down around the ring, while equatorial bonds extend outward from the ring, providing more space. The positioning of substituents affects the stability of the molecule, with equatorial positions generally being more favorable for larger groups.

Drawing Chair Conformations

When drawing chair conformations, it is essential to accurately represent the axial and equatorial bonds. The headrest and footrest orientation must be clearly indicated, as they determine the overall structure. Properly labeling the carbon atoms and ensuring the correct bond angles will help visualize the spatial arrangement of substituents, which is crucial for understanding reactivity and stability.

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