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 Configuration

Organic Chemistry

5. Chirality

R and S Configuration

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Problem 24d

Textbook Question

Prioritize the substituents at each chiral center and then, by comparing them to the models you created in Section 6.3.2, label the absolute configuration as R or S.
(d)

Verified step by step guidance

Step 1: Identify the chiral center in the molecule. A chiral center is a carbon atom bonded to four different substituents. In the given structure, the central carbon atom is bonded to a hydrogen (H), a methoxy group (CH3O), a chlorine atom (Cl), and a carbonyl group (C=O).

Step 2: Assign priorities to the substituents based on the Cahn-Ingold-Prelog (CIP) priority rules. The rules state that the substituent with the highest atomic number gets the highest priority. Here, chlorine (Cl) has the highest atomic number, so it is priority 1. The carbonyl group (C=O) is priority 2 because the carbon is double-bonded to oxygen. The methoxy group (CH3O) is priority 3, and hydrogen (H) is priority 4 because it has the lowest atomic number.

Step 3: Orient the molecule so that the lowest priority group (hydrogen, priority 4) is pointing away from you. This is typically represented as a dashed wedge in the structure.

Step 4: Determine the order of the remaining substituents (1, 2, 3) in a clockwise or counterclockwise direction. If the sequence is clockwise, the configuration is R. If the sequence is counterclockwise, the configuration is S.

Step 5: Compare the orientation and priority sequence to the models you created in Section 6.3.2 to confirm the absolute configuration as R or S.

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Key Concepts

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

Chirality

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. Chiral centers, typically carbon atoms bonded to four different substituents, are crucial in determining the molecule's stereochemistry. Understanding chirality is essential for labeling configurations as R or S.

Cahn-Ingold-Prelog Priority Rules

The Cahn-Ingold-Prelog (CIP) priority rules are a set of guidelines used to assign priority to substituents attached to a chiral center based on atomic number and connectivity. The substituent with the highest atomic number receives the highest priority. If two substituents have the same atomic number, the priority is determined by the next atoms in the substituent chain, which is vital for determining R or S configurations.

Absolute Configuration

Absolute configuration refers to the specific three-dimensional arrangement of atoms around a chiral center, designated as either R (rectus) or S (sinister). This designation is determined by the orientation of the highest priority substituents when viewed from a specific perspective. Correctly identifying the absolute configuration is crucial for understanding the molecule's behavior and reactivity in chemical reactions.

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