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 - Oxidative Cleavage

Organic Chemistry

28. Carbohydrates

Monosaccharides - Oxidative Cleavage

Previous problem

Problem 52k

Textbook Question

Predict the products obtained when D-galactose reacts with each reagent.
(k) excess HIO₄

Verified step by step guidance

Understand the reaction: Periodic acid (HIO4) is an oxidizing agent that cleaves vicinal diols (two hydroxyl groups on adjacent carbons) in carbohydrates. It breaks the C-C bond between the carbons bearing the hydroxyl groups, forming smaller carbonyl-containing fragments such as aldehydes or formic acid.

Analyze the structure of D-galactose: D-galactose is an aldohexose, meaning it has six carbons, with an aldehyde group at C1 and hydroxyl groups on the other carbons. Draw the Fischer projection of D-galactose to visualize the vicinal diols.

Identify the vicinal diols: In D-galactose, vicinal diols are present between C2-C3, C3-C4, C4-C5, and C5-C6. These are the sites where HIO4 will cleave the C-C bonds.

Determine the cleavage products: For each vicinal diol, the C-C bond is broken, and each carbon forms a carbonyl group. Depending on the position of the carbon, the products will be either formaldehyde (HCHO), formic acid (HCOOH), or a larger aldehyde/ketone.

Combine the results: After cleaving all vicinal diols in excess HIO4, the D-galactose molecule will be completely broken down into smaller fragments. Write out the specific products formed from each cleavage site to complete the reaction analysis.

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Key Concepts

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

D-Galactose Structure

D-galactose is a six-carbon aldose sugar with a specific stereochemistry. It contains an aldehyde group at one end and multiple hydroxyl groups, which influence its reactivity. Understanding its structure is crucial for predicting how it will react with various reagents, including oxidative agents like HIO4.

Periodic Acid Oxidation

Periodic acid (HIO4) is a strong oxidizing agent that cleaves vicinal diols and aldehydes. In the case of sugars, it can oxidatively cleave the carbon-carbon bonds adjacent to hydroxyl groups, leading to the formation of smaller aldehydes or ketones. This reaction is essential for understanding the products formed when d-galactose is treated with excess HIO4.

Reaction Mechanism

The reaction mechanism describes the step-by-step process by which reactants are converted into products. For d-galactose reacting with HIO4, the mechanism involves the formation of cyclic intermediates and subsequent cleavage of the sugar backbone. A clear grasp of these mechanisms helps in predicting the final products of the reaction.

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