Tandem grinding reactions involving aldol condensation and ...
Reactions Involving Free Radicals
description
Transcript of Reactions Involving Free Radicals
![Page 1: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/1.jpg)
Reactions Involving Free Radicals
![Page 2: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/2.jpg)
Free radical reactions involve one electron species, frequently generated by homolysis (shown below)
![Page 3: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/3.jpg)
![Page 4: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/4.jpg)
Radical reactions can be divided into three steps:1) Initiation2) Propagation3) Termination
![Page 5: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/5.jpg)
Weaker bonds are more readily cleaved by homolysis
![Page 6: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/6.jpg)
Some bonds can be cleaved by heating
![Page 8: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/8.jpg)
![Page 9: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/9.jpg)
![Page 10: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/10.jpg)
Radical Bromination
![Page 12: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/12.jpg)
![Page 13: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/13.jpg)
Allylic (and benzylic) bromination with NBS (N-Bromosuccinimide)
![Page 14: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/14.jpg)
NBS is regarded as a source of trace amounts of Br2 via the mechanism shown below.
![Page 15: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/15.jpg)
![Page 16: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/16.jpg)
![Page 17: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/17.jpg)
Reductions utilizing tributyltin hydride as a hydrogen atom donor
The Sn-H bond is relatively weak (82 kcal/mole), relative to the C-H bond (99 kcal/mole)By contrast, tin forms stronger bonds to bromine, iodine, and sulfur than does carbon.
Sn-S 111 kcalSn-Br 132 KcalSn-I 56 kcal
C-S 65 kcalC-Br 68 kcalC-I 51 kcal
![Page 18: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/18.jpg)
![Page 19: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/19.jpg)
![Page 20: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/20.jpg)
The Barton-McCombie Deoxygenation
![Page 21: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/21.jpg)
Mechanism
![Page 22: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/22.jpg)
![Page 23: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/23.jpg)
![Page 24: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/24.jpg)
![Page 25: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/25.jpg)
Radical Reaction with Allyltributylstannane
![Page 26: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/26.jpg)
![Page 27: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/27.jpg)
The Barton Decarboxylation
![Page 28: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/28.jpg)
![Page 29: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/29.jpg)
![Page 30: Reactions Involving Free Radicals](https://reader035.fdocuments.us/reader035/viewer/2022062323/568163e8550346895dd553fd/html5/thumbnails/30.jpg)