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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4:39 minutes

Problem 69

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.)

Verified step by step guidance

Analyze the structure of d-altrose: d-altrose is an aldohexose, meaning it contains six carbon atoms and an aldehyde functional group. It has four chiral centers, and its stereochemistry determines the orientation of its hydroxyl groups.

Understand the formation of pyranose and furanose rings: Pyranose rings are six-membered rings (five carbons and one oxygen), while furanose rings are five-membered rings (four carbons and one oxygen). Both forms result from the intramolecular reaction between the carbonyl group (C=O) and a hydroxyl group (-OH) on the sugar.

Consider the stability of the furanose form: In a five-membered furanose ring, the most stable arrangement occurs when adjacent substituents are trans to each other. Examine the stereochemistry of d-altrose to determine if this arrangement is possible and favorable.

Evaluate the stability of the pyranose form: In a six-membered pyranose ring, stability is influenced by the ability to adopt a chair conformation, minimizing steric hindrance and placing bulky groups in equatorial positions. Analyze the stereochemistry of d-altrose to determine if this conformation is more favorable than the furanose form.

Compare the two forms: Based on the stereochemical analysis and the stability considerations for both pyranose and furanose forms, predict which form is preferentially adopted by d-altrose. Remember that the most stable form will minimize steric hindrance and maximize favorable interactions.

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Key Concepts

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

Pyranose and Furanose Forms

Pyranose and furanose are two cyclic forms of monosaccharides. Pyranose is a six-membered ring structure, while furanose is a five-membered ring. The stability of these forms is influenced by steric interactions and the orientation of substituents around the ring. Understanding these structures is crucial for predicting the preferred form of sugars like d-altrose.

Chair and Boat Conformations

In the context of pyranose rings, the chair and boat conformations describe the spatial arrangement of atoms in the ring. The chair conformation is generally more stable due to minimized steric strain and torsional strain, allowing substituents to be positioned equatorially. This concept is essential for understanding how substituent orientation affects the stability of cyclic sugars.

Trans and Cis Substituent Orientation

The terms trans and cis refer to the relative positioning of substituents on a ring structure. In a trans arrangement, substituents are positioned on opposite sides, which often leads to lower steric hindrance and greater stability. This concept is particularly relevant when predicting the preferred form of d-altrose, as the hint suggests that the most stable arrangement favors trans orientations.

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