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 - Forming Cyclic Hemiacetals

Organic Chemistry

28. Carbohydrates

Monosaccharides - Forming Cyclic Hemiacetals

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3:18 minutes

Problem 47d

Textbook Question

Without referring to the chapter, draw the chair conformations of
(d) N-acetylglucosamine, glucose with the C2 oxygen atom replaced by an acetylated amino group.

Verified step by step guidance

Understand the structure of N-acetylglucosamine: It is a derivative of glucose where the hydroxyl group (-OH) on the C2 carbon is replaced by an acetylated amino group (-NHCOCH3). Familiarize yourself with the basic structure of glucose in its chair conformation to proceed.

Draw the basic chair conformation of glucose: Start by sketching the six-membered pyranose ring in its chair form. Label the carbon atoms from C1 to C6, ensuring the correct orientation of substituents (hydroxyl groups and hydrogen atoms) based on the D-glucose configuration.

Modify the C2 substituent: Replace the hydroxyl group (-OH) on the C2 carbon with an acetylated amino group (-NHCOCH3). Ensure that the orientation (axial or equatorial) of the substituent matches the original orientation of the hydroxyl group in glucose.

Verify the stereochemistry: Check that the stereochemistry of the other substituents (on C1, C3, C4, and C5) remains consistent with the D-glucose configuration. Ensure that the substituents alternate between axial and equatorial positions as appropriate.

Finalize the drawing: Clearly label the acetylated amino group on C2 and ensure that all substituents are correctly placed. Double-check the chair conformation for accuracy and stability, ensuring that bulky groups are in equatorial positions when possible to minimize steric hindrance.

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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 that minimizes steric strain and torsional strain. It allows for the most stable arrangement of substituents on the ring, with axial and equatorial positions that influence the molecule's overall stability and reactivity. Understanding how to draw and interpret chair conformations is crucial for analyzing the spatial arrangement of substituents in cyclic compounds.

Substituent Effects

Substituent effects refer to how different groups attached to a cyclohexane ring influence its stability and conformation. Groups can be bulky or small, and their position (axial or equatorial) can lead to steric hindrance or favorable interactions. Recognizing the impact of substituents, such as the acetylated amino group in N-acetylglucosamine, is essential for predicting the preferred chair conformation.

Anomeric Effect

The anomeric effect is a phenomenon observed in carbohydrate chemistry where the orientation of substituents at the anomeric carbon (the carbon derived from the carbonyl carbon during ring formation) can influence the stability of the molecule. This effect can lead to preferential axial or equatorial positioning of substituents, affecting the overall conformation of sugars like glucose and its derivatives. Understanding this effect is important for accurately drawing and predicting the behavior of sugar derivatives.

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Textbook Question

Two structures for the sugar glucose are shown on page 914. Interconversion of the open-chain and cyclic hemiacetal forms is catalyzed by either acid or base.

(b) The cyclic hemiacetal is more stable than the open-chain form, so very little of the open-chain form is present at equilibrium. Will an aqueous solution of glucose reduce Tollens reagent and give a positive Tollens test? Explain.