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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3:19 minutes

Problem 24

Textbook Question

Draw the α- and β-anomers of d-talopyranose. [The structure of talose is in Figure 27.11.]

Verified step by step guidance

Identify the structure of D-talose from the image. D-talose is an aldohexose with the configuration: C1 (CHO), C2 (OH on the left), C3 (OH on the left), C4 (OH on the left), C5 (OH on the right), and C6 (CH2OH).

Understand that pyranose forms are six-membered rings resulting from the reaction between the aldehyde group at C1 and the hydroxyl group at C5, forming a hemiacetal linkage.

To draw the α-anomer of D-talopyranose, form the pyranose ring by connecting C1 to C5. In the α-anomer, the OH group on C1 is trans to the CH2OH group at C5, meaning they are on opposite sides of the ring.

To draw the β-anomer of D-talopyranose, again form the pyranose ring by connecting C1 to C5. In the β-anomer, the OH group on C1 is cis to the CH2OH group at C5, meaning they are on the same side of the ring.

Ensure that the stereochemistry at C2, C3, and C4 remains the same as in the open-chain form, with the OH groups on C2, C3, and C4 positioned according to the original Fischer projection: C2 and C3 OH groups are equatorial, and C4 OH group is axial in the pyranose form.

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Key Concepts

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

Anomeric Carbon

The anomeric carbon is the carbon atom in a cyclic sugar that was the carbonyl carbon in the acyclic form. In the case of D-talopyranose, this is the carbon that forms the hemiacetal linkage, allowing for the formation of α- and β-anomers. The orientation of the hydroxyl group attached to this carbon determines the anomeric form.

Pyranose Ring

A pyranose ring is a six-membered ring structure consisting of five carbon atoms and one oxygen atom, resembling the structure of pyran. D-talopyranose forms such a ring when D-talose cyclizes, and understanding this structure is crucial for drawing the α- and β-anomers, as it dictates the spatial arrangement of the hydroxyl groups.

α- and β-Anomers

Anomers are isomers of cyclic saccharides that differ in configuration at the anomeric carbon. For D-talopyranose, the α-anomer has the hydroxyl group on the anomeric carbon trans to the CH2OH group, while the β-anomer has it cis. This distinction is essential for correctly drawing the two forms of D-talopyranose.

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Related Practice

Textbook Question

Which OH groups are in the axial position in each of the following?

a. β-D-idopyranose

b. α-D-allopyranose

Textbook Question

The aldaric acid of D-glucose forms two five-membered-ring lactones. Draw their structures.

Textbook Question

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

Textbook Question

In an aqueous solution, D-glucose exists in equilibrium with two six-membered ring compounds. Draw the structures of these compounds.

Textbook Question

Draw the α- and β-anomers of d-mannofuranose. [The structure of mannose is in Figure 27.11.]

Textbook Question

Draw each of the following:

a. β-D-talopyranose

b. α-D-idopyranose

Textbook Question

Predict whether D-altrose exists preferentially as a pyranose or a furanose. (Hint: In the most stable arrangement for a five-membered ring, all the adjacent substituents are trans.)

Textbook Question

Without referring to the chapter, draw the chair conformations of

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