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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5:47 minutes

Problem 84a,b

Textbook Question

Indicate whether each of the following structures is (R)-2-chlorobutane or (S)-2-chlorobutane:
a.
b.

Verified step by step guidance

Step 1: Identify the chiral center in each structure. In both structures (a and b), the carbon atom bonded to Br, H, CH3CH2, and CH2CH2CH3 is the chiral center.

Step 2: Assign priorities to the substituents around the chiral center based on the Cahn-Ingold-Prelog priority rules. The substituent with the highest atomic number gets the highest priority. Here, Br > CH2CH2CH3 > CH3CH2 > H.

Step 3: Orient the molecule so that the lowest priority group (H) is pointing away from you (on the dashed wedge). For structure (a), this orientation is already provided. For structure (b), you may need to mentally rotate the molecule to achieve this orientation.

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: Based on the analysis, assign the configuration (R or S) to each structure. Structure (a) and structure (b) will have their respective configurations determined by the above steps.

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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. A chiral molecule typically has a carbon atom bonded to four different substituents, leading to two distinct configurations known as enantiomers. In the case of 2-chlorobutane, the presence of the chlorine atom and the different alkyl groups creates chirality, resulting in (R) and (S) forms.

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, the substituents are ranked based on atomic number; higher atomic numbers receive higher priority. This ranking is crucial for determining the (R) or (S) configuration of chiral compounds, as it dictates the order in which the substituents are arranged.

R and S Nomenclature

R and S nomenclature is a system used to describe the configuration of chiral centers in organic molecules. The 'R' (rectus) designation indicates a clockwise arrangement of the highest priority substituents when viewed from a specific angle, while 'S' (sinister) indicates a counterclockwise arrangement. This nomenclature is essential for distinguishing between the two enantiomers of compounds like 2-chlorobutane, which can have different physical and chemical properties.

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