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 - Reduction (Alditols)

Organic Chemistry

28. Carbohydrates

Monosaccharides - Reduction (Alditols)

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5:43 minutes

Problem 13b

Textbook Question

What monosaccharide is reduced to two alditols, one of which is the alditol obtained from the reduction of
1. D-talose?
2. D-allose?

Verified step by step guidance

Understand the problem: The question asks which monosaccharide, when reduced, produces two alditols. One of these alditols must match the alditol obtained from the reduction of D-talose, and the other must match the alditol obtained from the reduction of D-allose. Reduction of a monosaccharide typically involves converting the aldehyde or ketone group into an alcohol group, forming an alditol.

Step 1: Recall the structure of D-talose and D-allose. Both are aldohexoses (six-carbon sugars with an aldehyde group). D-talose and D-allose differ in their stereochemistry at specific chiral centers. Write out their Fischer projections to visualize their structures.

Step 2: Understand the reduction process. When an aldohexose undergoes reduction, the aldehyde group (−CHO) at the top of the Fischer projection is converted into a primary alcohol group (−CH₂OH). This process does not alter the stereochemistry of the other chiral centers in the molecule.

Step 3: Identify the alditols formed from the reduction of D-talose and D-allose. Reduce the aldehyde group in each sugar to a primary alcohol group and determine the resulting alditols. These alditols will have the same stereochemistry as the original sugars at all chiral centers.

Step 4: Determine the common precursor monosaccharide. The question implies that there is a single monosaccharide that, when reduced, produces two alditols: one matching the alditol from D-talose and the other matching the alditol from D-allose. This suggests that the precursor monosaccharide is an epimer of both D-talose and D-allose, differing in stereochemistry at one or more chiral centers. Compare the structures of D-talose and D-allose to identify the common precursor.

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Key Concepts

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

Monosaccharides

Monosaccharides are the simplest form of carbohydrates, consisting of single sugar units. They serve as the building blocks for more complex carbohydrates and can exist in various forms, such as aldoses and ketoses. Understanding the structure and properties of monosaccharides is essential for grasping how they can be chemically modified, such as through reduction to form alditols.

Reduction of Sugars

Reduction of sugars involves the conversion of carbonyl groups (aldehydes or ketones) in monosaccharides to hydroxyl groups, resulting in the formation of alditols (sugar alcohols). This process is significant in organic chemistry as it alters the physical and chemical properties of the sugars, allowing for the study of their reactivity and potential applications in various fields, including food science and biochemistry.

Alditols

Alditols, or sugar alcohols, are the reduced forms of monosaccharides where the carbonyl group has been converted to a hydroxyl group. They are important in both biological systems and industrial applications, often used as sweeteners or humectants. Identifying specific alditols derived from particular monosaccharides, such as d-talose and d-allose, is crucial for understanding their metabolic pathways and potential uses.

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