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Topic: Free radical benzyl bromination of 2-Fluoro-4-Nitro toluene  (Read 2255 times)

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Offline SA3571

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Free radical benzyl bromination of 2-Fluoro-4-Nitro toluene
« on: January 10, 2013, 11:50:32 AM »
I am trying benzylic bromination of 2-Fluoro-4-Nitro toluene.
Conditions i have used so far:
1) NBS, AIBN, CCl4 reflux 7hrs
2) NBS, Benzoyl peroxide, chlorobenzene, reflux at 140C, 5hrs (then left O/N at 70C)

Everytime I get incomplete reaction...Major starting material....Only 20% product.

Any ideas??
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Offline discodermolide

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Re: Free radical benzyl bromination of 2-Fluoro-4-Nitro toluene
« Reply #1 on: January 10, 2013, 11:52:45 AM »
Add more AIBN or peroxide. Also you could shine a strong light on the reaction.
I assume your NBS is OK?
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Offline sjb

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Re: Free radical benzyl bromination of 2-Fluoro-4-Nitro toluene
« Reply #2 on: January 10, 2013, 12:22:29 PM »
Having carried out similar in the past, how are you visualising the reaction? From what I recall these run very close on TLC.
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Offline SA3571

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Re: Free radical benzyl bromination of 2-Fluoro-4-Nitro toluene
« Reply #3 on: January 10, 2013, 12:29:05 PM »
I could try and shine UV light to it. First reaction was done with 0.02eq of AIBN, second was done with 0.2eq of Benzoyl peroxide. NBS, AIBN and benzoyl peroxide bottles are new.

The reaction is analysed by TLC and I also separated the spots and checked by NMR.
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