Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 19m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 18m
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 Acids3h 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

Epimerization

Organic Chemistry

28. Carbohydrates

Epimerization

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4:01 minutes

Problem 23cWade - 9th Edition

Textbook Question

(a) Draw D-allose, the C3 epimer of glucose. (b) Draw D-talose, the C2 epimer of d-galactose

Verified step by step guidance

Step 1: Understand the concept of epimers. Epimers are sugars that differ only in the configuration around one specific carbon atom.

Step 2: Identify the structure of D-glucose. D-glucose is an aldohexose with the following stereochemistry: (2R, 3S, 4R, 5R).

Step 3: Draw D-allose by changing the configuration at C3 of D-glucose. This means you will invert the stereochemistry at C3 from S to R, resulting in (2R, 3R, 4R, 5R).

Step 4: Identify the structure of D-galactose. D-galactose is an aldohexose with the following stereochemistry: (2R, 3S, 4S, 5R).

Step 5: Draw D-talose by changing the configuration at C2 of D-galactose. This means you will invert the stereochemistry at C2 from R to S, resulting in (2S, 3S, 4S, 5R).

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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 carbohydrates, this means that two sugars can have the same molecular formula and differ only at one carbon atom's stereochemistry. Understanding epimers is crucial for distinguishing between similar sugars, such as D-allose and D-talose, which are epimers of glucose and D-galactose, respectively.

Fischer Projections

Fischer projections are a two-dimensional representation of three-dimensional organic molecules, particularly useful for depicting the stereochemistry of sugars. In these projections, vertical lines represent bonds that go back into the plane, while horizontal lines represent bonds that come out of the plane. Mastery of Fischer projections is essential for accurately drawing and interpreting the structures of carbohydrates like D-allose and D-talose.

D and L Configuration

The D and L configuration refers to the orientation of the hydroxyl group on the chiral carbon farthest from the carbonyl group in a sugar molecule. In D-sugars, this hydroxyl group is on the right in Fischer projections, while in L-sugars, it is on the left. Recognizing the D and L configurations is vital for correctly identifying and drawing the structures of sugars such as D-allose and D-talose.