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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1:40 minutes

Problem 27a

Textbook Question

Naproxen is a commercially available anti-inflammatory sold under the name Aleve.
(a) Assign the absolute configuration as R or S.

Verified step by step guidance

Identify the chiral center in the Naproxen molecule. A chiral center is a carbon atom bonded to four different groups.

Assign priorities to the four groups attached to the chiral center based on the Cahn-Ingold-Prelog (CIP) priority rules. These rules prioritize groups based on the atomic number of the atoms directly attached to the chiral center. If two atoms are the same, move outward along the chain until a difference is found.

Orient the molecule so that the group with the lowest priority (priority 4) is pointing away from you (into the plane of the paper or screen).

Determine the order of the remaining three groups (priority 1, 2, and 3) as you look at the molecule. Trace a path from priority 1 to 2 to 3. If the path is clockwise, the configuration is R (rectus). If the path is counterclockwise, the configuration is S (sinister).

Verify your assignment by double-checking the priority order and the orientation of the lowest-priority group to ensure the configuration is correctly assigned as either 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. Molecules that possess chirality typically have a carbon atom bonded to four different substituents, leading to two distinct configurations known as enantiomers. Understanding chirality is essential for determining the absolute configuration of compounds like Naproxen.

Cahn-Ingold-Prelog Priority Rules

The Cahn-Ingold-Prelog (CIP) priority rules are a set of guidelines used to assign priorities to the substituents attached to a chiral center. According to these rules, substituents are ranked based on atomic number, with higher atomic numbers receiving higher priority. This ranking is crucial for determining whether the configuration around a chiral center is R (rectus) or S (sinister).

R and S Configuration

The R and S configuration system is used to describe the absolute configuration of chiral centers in molecules. If the highest priority substituent is positioned clockwise when viewed from a specific perspective, the configuration is designated as R. Conversely, if the highest priority substituent is counterclockwise, it is designated as S. This system is vital for accurately describing the stereochemistry of compounds like Naproxen.

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Related Practice

Textbook Question

In Problem 5-3, you drew the enantiomers for a number of chiral compounds. Now go back and designate each asymmetric carbon atom as either (R) or (S).

(e) chlorocyclohexane

(f) cis-1,2-dichlorocyclobutane

Textbook Question

In Problem 5-3, you drew the enantiomers for a number of chiral compounds. Now go back and designate each asymmetric carbon atom as either (R) or (S).

(c)

(d) 1-bromo-2-methylbutane

Textbook Question

In Problem 5-3, you drew the enantiomers for a number of chiral compounds. Now go back and designate each asymmetric carbon atom as either (R) or (S).

(a)

(b)

Textbook Question

3,4-Dimethylpent-1-ene has the formula CH₂=CH—CH(CH₃)—CH(CH₃)₂. When pure (R)-3,4-dimethylpent-1-ene is treated with hydrogen over a platinum catalyst, the product is (S)-2,3-dimethylpentane.

c. The reactant is named (R), but the product is named (S). Does this name change imply a change in the spatial arrangement of the groups around the chiral center? So why does the name switch from (R) to (S)?

Textbook Question

Given the following IUPAC names, draw the corresponding structures.

(a) (R)-3-isopropyl-6-methylnon-1-ene

Textbook Question

Using IUPAC rules, name the following molecules.

(d)

Textbook Question

Given the name, draw the structure of the following compounds.

Textbook Question

Write structural formulas for the following compounds (includes both old- and new-style names).(j) vinylacetylene(k) (S)-3-methyl-1-penten-4-yne

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