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

Non-Carbon Chiral Centers

Organic Chemistry

5. Chirality

Non-Carbon Chiral Centers

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3:57 minutes

Problem 95

Textbook Question

Explain why the enantiomers of 1,2-dimethylaziridine can be separated even though one of the “groups” attached to nitrogen is a lone pair.
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Verified step by step guidance

Step 1: Recognize that 1,2-dimethylaziridine is a chiral molecule due to the presence of a stereogenic nitrogen atom. The nitrogen atom is bonded to three distinct groups: a methyl group, another methyl group attached to the aziridine ring, and a lone pair of electrons.

Step 2: Understand that the lone pair of electrons on nitrogen can act as a 'group' in determining chirality. This is because the spatial arrangement of the lone pair relative to the other substituents creates a non-superimposable mirror image, leading to enantiomers.

Step 3: Note that nitrogen inversion (the flipping of the lone pair through the plane of the molecule) is typically fast in many amines, which would make enantiomers indistinguishable. However, in the case of aziridines, the ring strain significantly slows down nitrogen inversion, allowing the enantiomers to exist as distinct, separable entities.

Step 4: Consider the physical and chemical properties of the enantiomers. Since enantiomers are non-superimposable mirror images, they will interact differently with chiral environments, such as polarized light or chiral reagents, enabling their separation.

Step 5: Conclude that the enantiomers of 1,2-dimethylaziridine can be separated because the nitrogen inversion is hindered by the strain of the aziridine ring, preserving the chirality and allowing the enantiomers to exist as stable, separable forms.

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Key Concepts

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

Enantiomers

Enantiomers are a type of stereoisomer that are non-superimposable mirror images of each other. They typically arise in chiral molecules, which have at least one carbon atom bonded to four different substituents. In the case of 1,2-dimethylaziridine, the presence of chiral centers leads to the formation of two distinct enantiomers, each exhibiting different spatial arrangements.

Chirality and Stereocenters

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image. A stereocenter, often a carbon atom, is bonded to four different groups, creating chirality. In 1,2-dimethylaziridine, the nitrogen atom can also contribute to chirality due to its lone pair, which can influence the spatial arrangement of the attached groups.

Separation of Enantiomers

Enantiomers can be separated through techniques such as chiral chromatography or by using chiral resolving agents. The unique spatial arrangement of the enantiomers allows them to interact differently with other chiral substances, enabling their separation. In the case of 1,2-dimethylaziridine, the lone pair on nitrogen can create a distinct environment that aids in the differentiation and separation of the enantiomers.

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