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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5:26 minutes

Problem 44b

Textbook Question

Ribonucleosides are not so easily hydrolyzed, requiring relatively strong acid. Using your mechanism for part (a), show why cytidine and adenosine (for example) are not so readily hydrolyzed. Explain why this stability is important for living organisms.

Verified step by step guidance

Identify the structure of ribonucleosides, such as cytidine and adenosine. These molecules consist of a ribose sugar linked to a nitrogenous base (cytosine or adenine) via a β-N-glycosidic bond.

Recall the mechanism for hydrolysis of glycosidic bonds. In acidic conditions, the hydrolysis typically involves protonation of the glycosidic oxygen, followed by cleavage of the bond to release the sugar and the base. This process is facilitated by the stability of the carbocation intermediate or transition state.

Analyze the electronic environment of the β-N-glycosidic bond in ribonucleosides. The nitrogen atom in the glycosidic bond is less electronegative than oxygen, making the bond less polarized and less susceptible to protonation. Additionally, the nitrogenous base does not stabilize a carbocation intermediate as effectively as oxygen in other glycosidic bonds (e.g., in DNA).

Explain why the resistance to hydrolysis is biologically significant. Ribonucleosides are components of RNA, which plays critical roles in protein synthesis and other cellular processes. Their stability ensures that RNA molecules remain intact under physiological conditions, allowing them to perform their functions effectively.

Conclude by emphasizing that the relatively strong acid required for hydrolysis of ribonucleosides reflects their chemical stability, which is essential for maintaining the integrity of genetic information and proper cellular function in living organisms.

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Key Concepts

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

Nucleoside Structure

Nucleosides consist of a nitrogenous base linked to a sugar (ribose in the case of ribonucleosides). The glycosidic bond between the base and the sugar is crucial for the stability of the nucleoside. In cytidine and adenosine, the specific orientation and electronic properties of the substituents contribute to the strength of this bond, making hydrolysis less favorable under mild conditions.

Acid-Base Chemistry

The hydrolysis of nucleosides involves breaking the glycosidic bond, which can be facilitated by protonation in acidic conditions. However, ribonucleosides like cytidine and adenosine have structural features that stabilize the bond against protonation and subsequent cleavage. Understanding the role of pH and the stability of intermediates is essential for explaining their resistance to hydrolysis.

Biological Significance of Stability

The stability of ribonucleosides is vital for cellular functions, as it ensures the integrity of RNA molecules during various biological processes. This stability prevents premature degradation, allowing for accurate protein synthesis and regulation of gene expression. In living organisms, maintaining the balance of nucleoside stability is crucial for proper cellular function and overall homeostasis.

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