Diamondback77
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Bromination of a strongly activated benzene ring
I am preparing to do a lab where we are working with a highly activated benzene ring (anisole). We are going to brominate it with a mixture of Br2 and
HBr. My question is, "Since Br2 is the electrophile, couldn't we use HCl instead of HBr as the acid?
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spirocycle
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what are your reaction conditions?
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Diamondback77
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No heat, just stir it at room temperature for ~ 20 minutes after combining all the reagents together.
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spirocycle
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where are your references that it will work with HBr and Br2?
usually that reaction is progressed with FeBr3 as a catalyst, and HBr is a product formed.
it would seem that adding a product of the bromination would slow or inhibit the reaction altogether.
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Nicodem
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Quote: Originally posted by Diamondback77  | | I am preparing to do a lab where we are working with a highly activated benzene ring (anisole). We are going to brominate it with a mixture of Br2 and
HBr. My question is, "Since Br2 is the electrophile, couldn't we use HCl instead of HBr as the acid? |
Why such an overkill reagent like Br2? And what role is HBr supposed to have? How do you expect to suppress dibromination under such harsh conditions?
What is the solvent? In what is HBr dissolved? Which concentration? Why not using some conditions/reagent appropriate to such nucleophilic substrates
like anisoles? For example, why not NBS in acetonitrile or anything similarly mild?
If you don't bother giving even the most basic information, how do you expect that members here will bother giving you a useful answer? Also,
according to our forum culture, you should open referenceless or unanswerable questions only in the Beginnings section where I'm moving this.
| Quote: Originally posted by spirocycle | where are your references that it will work with HBr and Br2?
usually that reaction is progressed with FeBr3 as a catalyst, and HBr is a product formed. |
What is this reference claiming the use of FeBr3 on anisole?
I really can't see how would you get a selective bromination of anisole under such harsh conditions.
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Nicodem
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Thread Moved
8-3-2011 at 09:07 |
vulture
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I once p-brominated anisole using NBS, CH2Cl2 and LiClO4/SiO2 dispersion. I was sceptical about this MO at first, but it worked.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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