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

Fischer Projection

Organic Chemistry

5. Chirality

Fischer Projection

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3:35 minutes

Problem 30a,b

Textbook Question

Give the stereochemical relationships between each pair of structures. Examples are same compound, structural isomers, enantiomers, and diastereomers. Which pairs could you (theoretically) separate by distillation or recrystallization?
(a)
(b)

Verified step by step guidance

Step 1: Analyze the stereochemical configuration of each pair of structures. For each structure, identify the arrangement of substituents around the chiral centers. Use the Cahn-Ingold-Prelog priority rules to assign R or S configurations to the chiral centers.

Step 2: Compare the configurations of the chiral centers between the two structures in each pair. If all chiral centers have opposite configurations, the structures are enantiomers. If some but not all chiral centers differ, the structures are diastereomers.

Step 3: Determine if the structures are identical by checking if the substituents and their spatial arrangements are the same. If they are identical, they represent the same compound.

Step 4: Evaluate whether the pairs can be separated by distillation or recrystallization. Enantiomers typically require chiral resolution techniques for separation, while diastereomers can often be separated by physical methods such as recrystallization or distillation due to differences in physical properties.

Step 5: Summarize the stereochemical relationships for each pair and indicate which pairs can theoretically be separated by distillation or recrystallization based on their physical property differences.

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Key Concepts

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

Stereoisomerism

Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. This can lead to different physical and chemical properties. The two main types of stereoisomers are enantiomers, which are non-superimposable mirror images, and diastereomers, which are not mirror images of each other.

Distillation and Recrystallization

Distillation and recrystallization are separation techniques used to purify compounds based on differences in their physical properties. Distillation relies on differences in boiling points, while recrystallization utilizes solubility differences at varying temperatures. These methods can effectively separate compounds that are not identical, such as structural isomers or diastereomers.

Structural Isomers vs. Stereoisomers

Structural isomers are compounds that have the same molecular formula but differ in the connectivity of their atoms, leading to different structural frameworks. In contrast, stereoisomers have the same connectivity but differ in the arrangement of atoms in space. Understanding these distinctions is crucial for analyzing the relationships between compounds and predicting their behavior in separation techniques.

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Textbook Question

Draw a Fischer projection for each compound. Remember that the cross represents an asymmetric carbon atom, and the carbon chain should be along the vertical, with the IUPAC numbering from top to bottom.

(e)