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

18. Aromaticity

Annulene

Organic Chemistry

18. Aromaticity

Annulene

Previous problemNext problem

6:12 minutes

Problem 6

Textbook Question

Make a model of cyclooctatetraene in the tub conformation. Draw this conformation, and estimate the angle between the p orbitals of adjacent pi bonds.

Verified step by step guidance

Step 1: Cyclooctatetraene is an eight-membered ring with alternating double bonds. In its tub conformation, the ring adopts a non-planar shape to minimize angle strain and steric hindrance.

Step 2: To draw the tub conformation, visualize the ring as having two opposite sides bent upward and downward, forming a shape similar to a bathtub. This conformation allows the molecule to relieve strain caused by the bond angles deviating from the ideal 120° of sp2 hybridized carbons.

Step 3: The p orbitals of adjacent pi bonds in cyclooctatetraene are not perfectly aligned due to the non-planar geometry. This misalignment reduces conjugation and makes the molecule non-aromatic.

Step 4: Estimate the angle between the p orbitals of adjacent pi bonds by considering the geometry of the tub conformation. The angle is typically less than 90° but greater than 0°, as the p orbitals are tilted relative to each other due to the bent structure.

Step 5: Use a molecular model kit or software to construct the tub conformation of cyclooctatetraene. This will help visualize the spatial arrangement of the p orbitals and confirm the estimated angle between them.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Cyclooctatetraene Structure

Cyclooctatetraene (COT) is an eight-membered cyclic hydrocarbon with alternating double bonds. Its unique structure allows it to adopt various conformations, with the 'tub' conformation being one of the most stable. This conformation minimizes steric strain and allows for a more favorable arrangement of the π bonds, which is crucial for understanding its reactivity and properties.

Conformation and Angle Between p Orbitals

In organic chemistry, conformation refers to the spatial arrangement of atoms in a molecule that can change due to rotation around single bonds. In the case of cyclooctatetraene, the angle between the p orbitals of adjacent π bonds is significant for determining the molecule's reactivity and stability. Estimating this angle helps in understanding the overlap of p orbitals and the resulting π bond character.

Aromaticity and Its Criteria

Aromaticity is a property of cyclic compounds that exhibit enhanced stability due to resonance and delocalization of π electrons. For a compound to be aromatic, it must be cyclic, planar, and follow Hückel's rule, which states that it must have (4n + 2) π electrons. Cyclooctatetraene is not aromatic in its tub conformation, as it does not meet these criteria, which is essential for understanding its chemical behavior.

Watch next

Master [6]annulene vs. [8]annulene with a bite sized video explanation from Johnny

Start learning