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Orest Reminsky

Brominating 4-methylbenzoic acid

Damien Leimbach  Follow
would I even need to protect it though?

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Curt Welch  Follow
CCl4, NBS, BPO(cat)

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David Wrixon  Follow
Do I get bromination on the Methylgroup or do I get it on the ring.

Which is the method to do. add bromine and Aluminiumbromide? Or use light to get it in the methylgroup.

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Bill Nugent  Follow
The problem would be how to protect the aromatic ring and also to stop the reaction after one bromine is substituted. Normally it goes through until tribromine derivate.

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Chris Gold  Follow
ok Wohl-Ziegler reaction.


http://onlinelibrary.wiley.com/doi/10.1002/9780470638859.conrr680/abstract

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Bryan Foong Zhi Chuan  Follow
This looks as though this should be known chemistry, known conditions, yields, isolation, etc. Why wouldn't you just follow a lit procedure.

I always heard two opposite sayings, five minutes in the library can save five days in the lab, and of course, five minutes in the lab can save five days in the library (or something like that). Experience tells us which rule to follow.

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Alan Garland  Follow
The methyl of the methyl ester won't be brominated. You can readily brominate the methyl group attached to the ring. You may see some ring bromination, but as Hunter2 asked, what conditions are you going to use?

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Military Aircraft  Follow
When I said some ring bromination I mean about 0.5-1% or less. It's something you may only pick up when doing the reaction on scale, >5-10 kg or so.

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Basecrete Global??  Follow
Quote from:
The problem would be how to protect the aromatic ring and also to stop the reaction after one bromine is substituted. Normally it goes through until tribromine derivate.


So how do you protect an aromatic ring? Did you mean the acidic group?
To the OP, you can always make an ester, it adds a step but may be worth the time. Give the bromination of the free acid a try and see what happens.

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Angelo Paredes  Follow
I dont think you can brominate the methyl of the methyl ester, or at least it will be unlikely, I think since it is next to an Oxygen which has two electron pairs the radical formed is too unstable (short lived) compared to radical on methyl which is stablized through resonance, I would imagine

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David Poling  Follow
Quote from:
If I planned to monobrominate the methyl position

You shouldn't plan to brominate the methyl position.

You should plan to find a catalog and buy some... it's not very expensive. If you want the ester, you can buy that too.

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Digital Tech & Business Innovation  Follow
I don't think you'll need to protect the carboxylic acid.  Radical bromination under the conditions you have given shouldn't mess with the acid, and I wouldn't worry about brominating the ring either. There are loads of examples in the literature in the presence of an unprotected acid (e.g. J Med Chem 2007, 5882).

 You definitely shouldn't use Friedel-Crafts conditions, as this will certainly brominate the ring and wouldn't touch the methyl group.

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