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

5. Chirality

R and S of Fischer Projections

Organic Chemistry

5. Chirality

R and S of Fischer Projections

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5:37 minutes

Problem 5

Textbook Question

Which configuration (R or S) does the bottom asymmetric carbon have for the D series of sugars? Which configuration for the L series?

Verified step by step guidance

Step 1: Identify the bottom asymmetric carbon in both D-Glucose and L-Glucose. This is the carbon atom directly attached to the CH₂OH group.

Step 2: Assign priorities to the substituents attached to the bottom asymmetric carbon based on the Cahn-Ingold-Prelog priority rules. The substituents are: CH₂OH (highest priority), OH, H, and the rest of the chain.

Step 3: Determine the spatial arrangement of the substituents around the bottom asymmetric carbon for D-Glucose. Visualize or use a model to determine whether the configuration follows a clockwise (R) or counterclockwise (S) rotation.

Step 4: Repeat the process for L-Glucose. Note that the substituents on the bottom asymmetric carbon are mirrored compared to D-Glucose, which will affect the configuration.

Step 5: Conclude the configurations for both D-Glucose and L-Glucose based on the analysis. For D-Glucose, the bottom asymmetric carbon typically has an R configuration, while for L-Glucose, it has an S configuration.

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Key Concepts

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

Chirality and Stereoisomers

Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image, leading to the existence of stereoisomers. In organic chemistry, chiral centers, typically carbon atoms with four different substituents, give rise to two configurations: R (rectus) and S (sinister). Understanding chirality is crucial for determining the specific configuration of sugars like D-Glucose and L-Glucose.

Fischer Projections

Fischer projections are a two-dimensional representation of three-dimensional organic molecules, particularly useful for depicting the stereochemistry of sugars. In these projections, vertical lines represent bonds going back into the plane, while horizontal lines represent bonds coming out. This format allows for easy identification of chiral centers and their configurations, essential for distinguishing between D and L forms of sugars.

D and L Configuration

The D and L notation for sugars is based on the orientation of the hydroxyl group (-OH) on the penultimate carbon (the second to last carbon) in the Fischer projection. If the -OH group is on the right side, the sugar is classified as D (from dexter, meaning right), while if it is on the left, it is classified as L (from laevus, meaning left). This classification is fundamental in carbohydrate chemistry and helps in understanding the biological roles of different sugar forms.

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