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

5. Chirality

Atropisomers

Organic Chemistry

5. Chirality

Atropisomers

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4:05 minutes

Problem 41a

Textbook Question

The original definition of meso is 'an achiral compound that has chiral diastereomers.' Our working definition of meso is 'an achiral compound that has chiral centers (usually asymmetric carbon atoms).' The working definition is much easier to apply, because we don't have to envision all possible chiral diastereomers of the compound. Still, the working definition is not quite as complete as the original definition.
a. Show how cis-cyclooctene is defined as a meso compound under the original definition, but not under our working definition. (Review Figure 5-19)

Verified step by step guidance

Step 1: Begin by understanding the original definition of a meso compound: 'an achiral compound that has chiral diastereomers.' This means the compound itself is achiral (it has a plane of symmetry or is superimposable on its mirror image), but it can have diastereomers that are chiral.

Step 2: Analyze cis-cyclooctene under the original definition. Cis-cyclooctene is achiral because it has a plane of symmetry. The molecule is symmetrical across the double bond, making it superimposable on its mirror image. However, if you envision possible diastereomers (e.g., trans-cyclooctene), these diastereomers are chiral due to the lack of symmetry in the trans configuration.

Step 3: Now consider the working definition of a meso compound: 'an achiral compound that has chiral centers (usually asymmetric carbon atoms).' Cis-cyclooctene does not have any chiral centers (asymmetric carbon atoms). The carbons involved in the double bond are sp2 hybridized and do not meet the criteria for chirality. Therefore, cis-cyclooctene does not qualify as meso under this definition.

Step 4: Refer to Figure 5-19 for visual clarification. The figure shows cis-cyclooctene and its mirror image, which are superimposable due to the plane of symmetry. This confirms its achirality. The figure also highlights the absence of chiral centers in the molecule, supporting the conclusion that it does not meet the working definition of meso.

Step 5: Conclude that cis-cyclooctene is defined as meso under the original definition because it is achiral and has chiral diastereomers (e.g., trans-cyclooctene). However, it does not meet the working definition of meso because it lacks chiral centers.

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Key Concepts

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

Meso Compounds

Meso compounds are defined as achiral molecules that contain multiple chiral centers but possess an internal plane of symmetry. This symmetry allows the molecule to be superimposable on its mirror image, thus rendering it achiral despite having chiral centers. Understanding this concept is crucial for identifying compounds like cis-cyclooctene, which can exhibit meso characteristics under certain conditions.

Chirality and Chiral Centers

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image, typically due to the presence of chiral centers, which are usually carbon atoms bonded to four different substituents. In the context of meso compounds, recognizing chiral centers is essential, as these centers contribute to the overall stereochemistry of the molecule, influencing whether it can be classified as meso or not.

Cis-Trans Isomerism

Cis-trans isomerism is a form of stereoisomerism where the spatial arrangement of substituents around a double bond or ring structure differs. In the case of cis-cyclooctene, the arrangement of hydrogen atoms and the double bond leads to distinct geometric configurations. This isomerism plays a significant role in determining the compound's chirality and whether it meets the criteria for being classified as a meso compound.

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