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

11. Radical Reactions

Free Radical Halogenation

Organic Chemistry

11. Radical Reactions

Free Radical Halogenation

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8:57 minutes

Problem 60

Textbook Question

Haloalkanes can be reduced to alkanes using radical reactions involving Bu₃SnH and a catalytic amount of AIBN. Suggest a mechanism for this reaction. [Pay close attention to the bonds formed and broken in developing your mechanism.]

Verified step by step guidance

Begin by understanding the role of AIBN (azobisisobutyronitrile) in the reaction. AIBN is a radical initiator that decomposes upon heating to form two 2-cyanoprop-2-yl radicals. This step is crucial as it initiates the radical chain reaction.

The 2-cyanoprop-2-yl radical generated from AIBN abstracts a hydrogen atom from Bu₃SnH, forming a Bu₃Sn radical. This step is important as it generates the tin radical necessary for the propagation of the radical chain reaction.

The Bu₃Sn radical then abstracts the bromine atom from the haloalkane, forming an alkyl radical and Bu₃SnBr. This step involves the breaking of the C-Br bond and the formation of a new C-Sn bond.

The alkyl radical formed in the previous step abstracts a hydrogen atom from another molecule of Bu₃SnH, forming the alkane product and regenerating the Bu₃Sn radical. This step completes the radical chain reaction and ensures the continuation of the process.

Finally, the regenerated Bu₃Sn radical can continue to react with more haloalkane molecules, propagating the radical chain reaction. This step highlights the catalytic nature of the reaction, as the Bu₃Sn radical is continuously regenerated.

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Key Concepts

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

Radical Initiation

Radical initiation is the first step in radical reactions where radicals are generated. In this mechanism, AIBN (azobisisobutyronitrile) acts as a radical initiator, decomposing upon heating to form nitrogen gas and two 2-cyanoprop-2-yl radicals. These radicals are crucial for starting the chain reaction by abstracting hydrogen from Bu₃SnH, generating a tin radical.

Radical Propagation

Radical propagation involves the reaction of radicals with stable molecules to form new radicals, continuing the chain reaction. The tin radical generated in the initiation step abstracts the halogen atom from the haloalkane, forming an alkyl radical and Bu₃SnBr. The alkyl radical then reacts with Bu₃SnH, regenerating the tin radical and forming the alkane product.

Radical Termination

Radical termination occurs when two radicals combine to form a stable molecule, effectively ending the chain reaction. In this mechanism, termination can happen when two alkyl radicals or two tin radicals combine, although the primary focus is on the propagation steps that lead to the desired alkane product. Termination ensures that the reaction does not continue indefinitely, stabilizing the system.

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