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 - Haworth Projections

Organic Chemistry

28. Carbohydrates

Monosaccharides - Haworth Projections

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Problem 7

Textbook Question

Draw the Haworth projection for the cyclic structure of D-mannose by laying down the Fischer projection.

Verified step by step guidance

Start by identifying the Fischer projection of D-mannose. D-mannose is an aldohexose, meaning it has six carbons and an aldehyde group at the top. The hydroxyl (-OH) groups on the chiral carbons are arranged as follows: on the second carbon, the -OH is on the left; on the third carbon, the -OH is on the right; on the fourth carbon, the -OH is on the left; and on the fifth carbon, the -OH is on the right.

Determine the type of cyclic structure D-mannose forms. D-mannose typically forms a six-membered ring (pyranose) by reacting the aldehyde group on carbon 1 with the hydroxyl group on carbon 5, creating a hemiacetal linkage.

Convert the Fischer projection into a Haworth projection. To do this, orient the Fischer projection so that the groups on the right side of the Fischer projection point downward in the Haworth projection, and the groups on the left side point upward. For D-mannose, the -OH on carbon 2 points upward, the -OH on carbon 3 points downward, the -OH on carbon 4 points upward, and the -CH2OH group on carbon 5 points upward.

Add the anomeric carbon configuration. The anomeric carbon (carbon 1) can have two possible configurations: alpha (α) or beta (β). In the α-anomer, the -OH group on carbon 1 points downward, while in the β-anomer, the -OH group on carbon 1 points upward. Decide which anomer to draw based on the problem's requirements or draw both if unspecified.

Complete the Haworth projection by ensuring all atoms and bonds are correctly represented. Verify that the oxygen atom in the ring is between carbons 1 and 5, and that the substituents on each carbon are correctly positioned based on the rules for converting Fischer to Haworth projections.

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Key Concepts

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

Haworth Projection

The Haworth projection is a way of representing the cyclic forms of sugars, showing the arrangement of atoms in a three-dimensional perspective. It illustrates the cyclic structure of monosaccharides, where the carbon atoms are represented in a ring format, and the hydroxyl groups and other substituents are positioned above or below the plane of the ring. This representation is crucial for understanding the stereochemistry and reactivity of carbohydrates.

Fischer Projection

The Fischer projection is a two-dimensional representation of organic molecules, particularly sugars, that displays the configuration of chiral centers. In this format, the vertical lines represent bonds going back into the plane, while horizontal lines represent bonds coming out of the plane. Converting a Fischer projection to a Haworth projection involves identifying the orientation of substituents around the chiral centers to accurately depict the cyclic structure.

D-Mannose

D-Mannose is a naturally occurring sugar and an epimer of glucose, differing at the C2 carbon. It is an aldohexose, meaning it contains six carbon atoms and an aldehyde functional group. Understanding the specific stereochemistry of D-mannose is essential for accurately drawing its cyclic form, as the orientation of hydroxyl groups in the Fischer projection directly influences the resulting Haworth projection.

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