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

Monosaccharide

Organic Chemistry

28. Carbohydrates

Monosaccharide

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2:49 minutes

Problem 8a

Textbook Question

How many stereoisomers are possible for a. a ketoheptose?

Verified step by step guidance

Understand the structure of a ketoheptose: A ketoheptose is a seven-carbon sugar (heptose) with a ketone functional group. The ketone group is typically located at the second carbon (C-2), making it a 2-ketoheptose.

Determine the number of chiral centers: In a ketoheptose, the ketone group at C-2 is not a chiral center. The remaining five carbons (C-3 to C-7) each have a hydroxyl (-OH) group and a hydrogen (-H) attached, making them potential chiral centers. Therefore, there are 5 chiral centers in a ketoheptose.

Apply the formula for the number of stereoisomers: The number of stereoisomers for a molecule with 'n' chiral centers is given by the formula \( 2^n \). For a ketoheptose with 5 chiral centers, substitute \( n = 5 \) into the formula.

Calculate \( 2^5 \): This step involves determining the total number of stereoisomers by evaluating \( 2^5 \), which represents the possible combinations of configurations (R or S) at each chiral center.

Conclude the total number of stereoisomers: The result from the previous step gives the total number of stereoisomers possible for a ketoheptose, including both enantiomers and diastereomers.

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Key Concepts

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

Stereoisomerism

Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. This can lead to different physical and chemical properties. In carbohydrates, stereoisomers arise due to the presence of chiral centers, which are carbon atoms bonded to four different groups.

Chirality and Chiral Centers

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. A chiral center, typically a carbon atom, is bonded to four distinct substituents, leading to two possible configurations (enantiomers). The number of chiral centers in a molecule directly influences the number of stereoisomers it can have.

Calculating Stereoisomers

The total number of stereoisomers for a compound can be calculated using the formula 2^n, where n is the number of chiral centers. For a ketoheptose, which has multiple chiral centers, this formula helps determine the maximum number of stereoisomers possible. Additionally, the presence of any symmetry in the molecule can reduce the total count of unique stereoisomers.

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