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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3:23 minutes

Problem 26

Textbook Question

Why is only a trace amount of acid used in the formation of an N-glycoside?

Verified step by step guidance

Understand the context: The formation of an N-glycoside involves the reaction of a sugar (typically in its cyclic hemiacetal form) with an amine. This reaction is acid-catalyzed, meaning a small amount of acid is used to facilitate the process.

Recognize the role of the acid: The acid protonates the hydroxyl group of the sugar, making it a better leaving group. This step is crucial for the formation of the oxocarbenium ion intermediate, which is highly reactive and facilitates the nucleophilic attack by the amine.

Consider the sensitivity of the reactants: Sugars are prone to degradation under strongly acidic conditions, such as hydrolysis or dehydration reactions. Using only a trace amount of acid minimizes the risk of side reactions and ensures the sugar remains intact during the reaction.

Acknowledge the catalytic nature of the acid: Since the acid is not consumed in the reaction, only a catalytic (trace) amount is needed to continuously facilitate the formation of the oxocarbenium ion and drive the reaction forward.

Conclude the reasoning: Using a trace amount of acid ensures that the reaction proceeds efficiently while avoiding excessive degradation of the sugar or other unwanted side reactions, leading to the selective formation of the N-glycoside.

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Key Concepts

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

N-glycoside Formation

N-glycosides are formed when a sugar molecule reacts with an amine, resulting in a glycosidic bond. This reaction typically requires an acid catalyst to activate the sugar, making it more electrophilic and facilitating the nucleophilic attack by the amine. Understanding this process is crucial for grasping why specific conditions, such as the use of trace amounts of acid, are employed.

Acid Catalysis

Acid catalysis involves the use of an acid to increase the rate of a chemical reaction. In the context of N-glycoside formation, a small amount of acid is sufficient to protonate the sugar, enhancing its reactivity without overwhelming the reaction. Excess acid can lead to side reactions or degradation of the sugar, making controlled use essential.

Selectivity in Organic Reactions

Selectivity refers to the preference of a reaction to produce a particular product over others. In the formation of N-glycosides, using only a trace amount of acid helps ensure that the desired glycosidic bond forms preferentially, minimizing by-products. This selectivity is vital for achieving high yields and purity in organic synthesis.

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