Reaction Review 28 - Allylic and Benzylic Brominations Using NBS PDF

Title	Reaction Review 28 - Allylic and Benzylic Brominations Using NBS
Course	Introduction To Organic Chemistry I
Institution	University of North Carolina at Chapel Hill
Pages	2
File Size	188.2 KB
File Type	PDF
Total Downloads	33
Total Views	121

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Download Reaction Review 28 - Allylic and Benzylic Brominations Using NBS PDF

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Rxn Review #28 – Allylic and Benzylic Brominations Using NBS The reagent n-bromosuccinimide is a specialized reagent used to do radical brominations at allylic and benzylic positions. It is preferred over using Br2 and light/heat, since that method will provide mixed products from electrophilic additions (with allylic systems).

The NBS provides a very low level of molecular bromine (Br2) which lessens the interferences, allowing the radical addition to prevail. Mechanism (allylic):

Mechanism (benzylic):

Note: For both benzylic and allyic mechanisms with NBS, there is the possibility of resonance with the intermediate radical. When this is the case, you often see mixed products. See example below:...