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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1:50 minutes

Problem 105a,b

Textbook Question

What is the configuration of each of the asymmetric centers in the following compounds?
a.
b.

Verified step by step guidance

Step 1: Identify the asymmetric centers in each compound. An asymmetric center is a carbon atom bonded to four different groups. In compound (a), the central carbon is bonded to Br, OH, CH3, and H. In compound (b), the central carbon is bonded to Cl, CH3, CH2Cl, and H.

Step 2: Assign priorities to the substituents around the asymmetric center based on the Cahn-Ingold-Prelog (CIP) priority rules. The priority is determined by the atomic number of the atoms directly attached to the asymmetric center. For compound (a), the priorities are: Br (highest, atomic number 35), OH (atomic number 8), CH3 (atomic number 6), and H (lowest, atomic number 1). For compound (b), the priorities are: Cl (highest, atomic number 17), CH2Cl (atomic number 6 with Cl attached), CH3 (atomic number 6), and H (lowest, atomic number 1).

Step 3: Orient the molecule so that the lowest priority group (H) is pointing away from you. For compound (a), the H is already pointing away (on the dashed wedge). For compound (b), the H is on the horizontal bond, so you may need to mentally rotate the molecule to visualize it correctly.

Step 4: Determine the sequence of the remaining three groups (1, 2, 3) in order of priority. Trace the path from the highest priority group to the second and then to the third. For compound (a), trace from Br → OH → CH3. For compound (b), trace from Cl → CH2Cl → CH3.

Step 5: Assign the configuration as R or S based on the direction of the sequence. If the sequence is clockwise, the configuration is R. If the sequence is counterclockwise, the configuration is S. Use the orientation and priority sequence determined in the previous steps to assign the configuration for each compound.

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Key Concepts

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

Asymmetric Centers

Asymmetric centers, or chiral centers, are carbon atoms bonded to four different substituents, leading to non-superimposable mirror images known as enantiomers. Identifying these centers is crucial for determining the stereochemistry of a compound, as the spatial arrangement of these substituents affects the compound's properties and reactivity.

Cahn-Ingold-Prelog Priority Rules

The Cahn-Ingold-Prelog (CIP) priority rules are a systematic method for assigning priorities to the substituents attached to an asymmetric center. By comparing the atomic numbers of the atoms directly bonded to the chiral carbon, one can determine the order of priority, which is essential for assigning the R or S configuration to the chiral centers.

Stereochemistry

Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this arrangement affects their chemical behavior. Understanding stereochemistry is vital for analyzing the configuration of asymmetric centers, as it influences the physical and biological properties of compounds, including their interactions with enzymes and receptors.

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