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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6:00 minutes

Problem 59

Textbook Question

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

Verified step by step guidance

Understand the problem: Aldaric acids are dicarboxylic acids derived from aldoses by oxidizing both the aldehyde group and the terminal primary alcohol group to carboxylic acids. For D-glucose, this means both the C1 and C6 carbons are oxidized to carboxylic acids. Lactones are cyclic esters formed when a hydroxyl group reacts with a carboxylic acid group within the same molecule.

Identify the functional groups in D-glucose: D-glucose has hydroxyl (-OH) groups on carbons C2, C3, C4, and C5. After oxidation to aldaric acid, the molecule will have carboxylic acid groups at C1 and C6, and hydroxyl groups at the other carbons.

Determine the possible lactone formations: A five-membered ring lactone (γ-lactone) forms when the hydroxyl group on C4 or C5 reacts with the carboxylic acid group on C1. This creates two possible structures depending on which hydroxyl group participates in the reaction.

Draw the first lactone structure: For the first lactone, the hydroxyl group on C4 reacts with the carboxylic acid group on C1. This forms a five-membered ring with the following atoms: C1 (carboxylic acid carbon), O (from the hydroxyl group on C4), C4, C3, and C2. The remaining hydroxyl groups and the carboxylic acid group on C6 remain unchanged.

Draw the second lactone structure: For the second lactone, the hydroxyl group on C5 reacts with the carboxylic acid group on C1. This forms a five-membered ring with the following atoms: C1 (carboxylic acid carbon), O (from the hydroxyl group on C5), C5, C4, and C3. The remaining hydroxyl groups and the carboxylic acid group on C6 remain unchanged.

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Key Concepts

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

Aldaric Acid

Aldaric acids are a type of dicarboxylic acid derived from aldoses, where both the aldehyde and the terminal alcohol group are oxidized to carboxylic acids. In the case of d-glucose, the aldaric acid formed is d-glucaric acid. Understanding the structure of aldaric acids is crucial for recognizing how they can undergo cyclization to form lactones.

Lactone Formation

Lactones are cyclic esters formed when a hydroxyl group reacts with a carboxylic acid group within the same molecule, leading to the loss of water. In the case of d-glucose aldaric acid, two different five-membered lactones can be formed depending on which hydroxyl group participates in the reaction. This concept is essential for predicting the structures of the resulting lactones.

Five-Membered Ring Structures

Five-membered ring structures, such as furanoses, are common in carbohydrate chemistry. They are formed when a sugar molecule cyclizes, creating a stable ring that can influence the molecule's reactivity and properties. Recognizing the formation of these rings from aldaric acids is key to drawing the correct structures of the lactones derived from d-glucose.

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