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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2:40 minutes

Problem 47c

Textbook Question

Without referring to the chapter, draw the chair conformations of
(c) β-D-galactopyranose (the C4 epimer of glucose).

Verified step by step guidance

Understand the structure of β-D-galactopyranose: It is a six-membered cyclic sugar (pyranose form) with the hydroxyl group at the anomeric carbon (C1) in the beta configuration (equatorial position). Galactose is the C4 epimer of glucose, meaning the configuration of the hydroxyl group at C4 is different from that of glucose.

Draw the basic chair conformation of a six-membered ring: Start by sketching a cyclohexane chair structure. Label the carbon atoms from C1 to C6 in a clockwise direction, with C1 at the top right corner.

Place the substituents on the ring: Add the hydroxyl groups and hydrogen atoms to each carbon based on the stereochemistry of β-D-galactopyranose. For β-D-galactopyranose: (1) At C1, place the hydroxyl group in the equatorial position and the hydrogen in the axial position. (2) At C2, place the hydroxyl group in the equatorial position. (3) At C3, place the hydroxyl group in the axial position. (4) At C4, place the hydroxyl group in the axial position (this is the key difference from glucose). (5) At C5, place the hydroxyl group in the equatorial position. (6) At C6, place the CH2OH group in the equatorial position.

Verify the stereochemistry: Double-check that the substituents match the stereochemistry of β-D-galactopyranose, ensuring that the hydroxyl group at C4 is in the axial position, distinguishing it from glucose.

Finalize the drawing: Clearly label the chair conformation with all substituents, ensuring the beta configuration at C1 and the correct stereochemistry at all other carbons. This will give you the chair conformation of β-D-galactopyranose.

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Key Concepts

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

Chair Conformation

The chair conformation is a three-dimensional representation of cyclohexane and its derivatives, which minimizes steric strain and torsional strain. In this conformation, the carbon atoms are arranged in a way that allows for staggered bonds, making it the most stable form of cyclohexane. Understanding chair conformations is crucial for visualizing the spatial arrangement of substituents on cyclic structures, such as sugars.

Anomeric Carbon

The anomeric carbon is the carbon atom in a sugar that is derived from the carbonyl carbon during the formation of a cyclic structure. In pyranoses, this carbon is typically the first carbon (C1) and is crucial for determining the alpha or beta configuration of the sugar. The orientation of the hydroxyl group on the anomeric carbon relative to the CH2OH group defines whether the sugar is in the alpha or beta form, which is essential for understanding the properties of carbohydrates.

Epimers

Epimers are a specific type of diastereomer that differ in configuration at only one stereogenic center. In the case of b-D-galactopyranose and glucose, they differ at the C4 position, making them C4 epimers. Recognizing epimers is important in carbohydrate chemistry as it influences the physical and chemical properties of sugars, including their reactivity and biological roles.

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