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

28. Carbohydrates

Monosaccharides - Cyclization

Organic Chemistry

28. Carbohydrates

Monosaccharides - Cyclization

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Problem 9

Textbook Question

Talose is the C4 epimer of mannose. Draw the chair conformation of D-talopyranose.

Verified step by step guidance

Understand the problem: Talose is the C4 epimer of mannose, meaning that the configuration of the hydroxyl group (-OH) on the fourth carbon (C4) is inverted compared to mannose. We are tasked with drawing the chair conformation of D-talopyranose, which is the cyclic form of D-talose in a six-membered ring structure.

Start by determining the Fischer projection of D-talose. Since it is the C4 epimer of mannose, copy the Fischer projection of D-mannose and invert the configuration of the hydroxyl group on C4. Ensure the other stereocenters (C2, C3, and C5) remain the same as in D-mannose.

Convert the Fischer projection of D-talose into a Haworth projection for D-talopyranose. To do this, cyclize the molecule by forming a bond between the hydroxyl group on C5 and the carbonyl carbon (C1), creating a hemiacetal. Assign the anomeric configuration (α or β) based on the orientation of the newly formed hydroxyl group on C1.

Translate the Haworth projection into a chair conformation. Place the six-membered ring in a chair form, ensuring that the substituents (hydroxyl groups and hydrogen atoms) on each carbon are positioned either axially (parallel to the ring's axis) or equatorially (perpendicular to the ring's axis). Use the stereochemistry from the Haworth projection to determine the correct positions of the substituents.

Double-check the stereochemistry of the chair conformation to ensure it matches the original Fischer projection of D-talose. Verify that the hydroxyl group on C4 is in the correct position to reflect the epimeric relationship with mannose, and confirm that the other substituents are consistent with the D-talose configuration.

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Key Concepts

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

Epimers

Epimers are a specific type of diastereomer that differ in configuration at only one stereogenic center. In the case of talose and mannose, they are both aldohexoses that differ at the C4 carbon. Understanding epimerism is crucial for distinguishing between similar sugars and predicting their chemical behavior.

Chair Conformation

The chair conformation is a three-dimensional representation of cyclohexane and its derivatives, which minimizes steric strain and torsional strain. For sugars like D-talopyranose, drawing the chair conformation helps visualize the spatial arrangement of substituents around the ring, which is essential for understanding their reactivity and interactions.

Pyranose Structure

Pyranose refers to a six-membered ring structure formed by the cyclization of monosaccharides, typically involving an aldehyde or ketone group. In D-talopyranose, the ring structure is stabilized by the formation of an acetal linkage, which is important for its stability and biological function. Recognizing the pyranose form is key to understanding carbohydrate chemistry.

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