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

16. Conjugated Systems

Sigmatropic Rearrangement

Organic Chemistry

16. Conjugated Systems

Sigmatropic Rearrangement

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6:13 minutes

Problem 18a

Textbook Question

a. Will thermal 1,3-migrations of carbon occur with retention or inversion of configuration?

Verified step by step guidance

Understand the concept of a 1,3-migration: A 1,3-migration involves the movement of a substituent (in this case, a carbon group) from one atom to another within a molecule, specifically over a distance of three atoms. This process often occurs under thermal conditions and involves a concerted mechanism.

Recognize the stereochemical implications: In a concerted reaction mechanism, the migration of the substituent and the reorganization of bonding orbitals occur simultaneously. This means that the stereochemistry of the migrating group is directly influenced by the orbital alignment during the transition state.

Analyze the orbital interactions: During a thermal 1,3-migration, the reaction typically proceeds through a suprafacial pathway (on the same face of the molecule) if the system has a favorable orbital overlap. This suprafacial migration leads to retention of configuration at the migrating carbon center.

Consider the Woodward-Hoffmann rules: These rules help predict the stereochemical outcome of pericyclic reactions. For a thermal 1,3-migration, the reaction follows the conservation of orbital symmetry, which supports retention of configuration for the migrating group.

Conclude the stereochemical outcome: Based on the concerted mechanism, orbital interactions, and the Woodward-Hoffmann rules, thermal 1,3-migrations of carbon occur with retention of configuration at the migrating carbon center.

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Key Concepts

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

1,3-Migration Mechanism

1,3-migrations refer to the rearrangement of a substituent from one carbon atom to another that is three positions away in a molecule. This process often occurs in the context of rearrangements involving carbocations or radical intermediates. Understanding the mechanism is crucial for predicting the stereochemical outcome of the migration.

Retention vs. Inversion of Configuration

Retention and inversion of configuration describe how the spatial arrangement of atoms around a chiral center changes during a reaction. Retention means the configuration remains the same, while inversion indicates a switch in the arrangement. The stereochemical outcome of a migration can depend on the nature of the intermediates and the reaction conditions.

Thermal vs. Photochemical Reactions

Thermal reactions occur at elevated temperatures and typically involve the breaking and forming of bonds without the need for light. In contrast, photochemical reactions are driven by light energy. The conditions under which a 1,3-migration occurs can influence whether the reaction leads to retention or inversion of configuration, making it essential to consider the thermal context.

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