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 - N-Glycosides

Organic Chemistry

28. Carbohydrates

Monosaccharides - N-Glycosides

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4:07 minutes

Problem 44a

Textbook Question

An aliphatic aminoglycoside is relatively stable to base, but it is quickly hydrolyzed by dilute acid. Propose a mechanism for the acid-catalyzed hydrolysis.

Verified step by step guidance

Step 1: Recognize that the reaction involves acid-catalyzed hydrolysis of an aliphatic aminoglycoside. The structure provided shows a glycosidic bond between a sugar moiety and an amine group (R2N). Acid catalysis typically involves protonation of the oxygen atom in the glycosidic bond, making it more susceptible to cleavage.

Step 2: Protonation occurs at the oxygen atom of the glycosidic bond by hydronium ion (H3O+). This increases the electrophilicity of the carbon atom attached to the oxygen, making it more prone to nucleophilic attack or bond cleavage.

Step 3: The protonated glycosidic bond undergoes cleavage. The bond between the sugar and the amine group breaks, resulting in the formation of a positively charged amine (R2NH2+) and a sugar molecule. This step is facilitated by the acidic environment.

Step 4: The sugar molecule formed may undergo further protonation or rearrangement depending on the reaction conditions, but the primary products are the free sugar and the protonated amine group.

Step 5: The mechanism highlights the role of acid in destabilizing the glycosidic bond and promoting hydrolysis. This explains why the aminoglycoside is stable in base but hydrolyzed quickly in acid.

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Key Concepts

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

Acid-Catalyzed Hydrolysis

Acid-catalyzed hydrolysis is a reaction where an acid donates protons (H+) to facilitate the breaking of chemical bonds in a molecule, leading to the formation of new products. In the case of aminoglycosides, the presence of hydronium ions (H3O+) enhances the nucleophilicity of water, allowing it to attack the glycosidic bond, resulting in the cleavage of the molecule into simpler components, such as sugar and an amine.

Aminoglycosides Structure

Aminoglycosides are a class of antibiotics characterized by their amino sugar components and glycosidic linkages. Their structure typically includes one or more amino groups attached to sugar moieties, which are crucial for their biological activity. Understanding the structural features of aminoglycosides is essential for predicting their reactivity, particularly how they respond to acidic conditions during hydrolysis.

Mechanism of Hydrolysis

The mechanism of hydrolysis involves a series of steps where the acid protonates the leaving group, making it a better leaving entity. This is followed by the nucleophilic attack of water on the electrophilic carbon, leading to the formation of a carbocation intermediate. The subsequent steps involve the breakdown of the carbocation and the release of the products, which in this case are a sugar and a protonated amine (R2NH2+).

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