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Topic: Friedel-Crafts Acylation of Dihalobenzenes?  (Read 6388 times)

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Offline Stri

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Friedel-Crafts Acylation of Dihalobenzenes?
« on: April 07, 2010, 10:55:04 AM »
My most recent Organic exam had a question asking for the product of friedel-crafts acylation of p-dichlorobenzene. I said that no reaction occurred, while my teacher said that substitution will occur.

My text states that friedel-crafts reactions will not take place on a benzene that is less activating than a monohalobenzene, which is the reasoning behind my answer choice. I cannot seem to find any sources online that corroborate this, however. I also have not found much stating that acylation will occur.

Is a dihalobenzene activating enough for friedel-crafts, and is my text incorrect?

Thank you very much

Offline sHaY

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Re: Friedel-Crafts Acylation of Dihalobenzenes?
« Reply #1 on: April 07, 2010, 05:52:28 PM »
OK, you got 2 Br para to each other, let's start from the basic point of view, Br is a weak deactivator but nevertheless an ortho-para director, recall the you cannot Acylate or Alkalate a strongly deactivated ring(NO2 attached), that being said you would probably see the reaction occurs in the ortho position with respect to the Br.

Offline orgopete

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Re: Friedel-Crafts Acylation of Dihalobenzenes?
« Reply #2 on: April 08, 2010, 01:11:27 AM »
This is a good question, but difficult to give a definitive answer to. In doing a Google search, it is easy to find that ortho-dichlorobenzene is an inert solvent for acylation reactions. I did not see any examples of it being acylated. I believe your answer is probably correct, but it is difficult to prove that substitution cannot occur (if that is what your teacher is asserting). I would probably raise the issue with your teacher and ask for a literature example of the reaction.

Those with access to SciFinder could do this search for us by searching for p-dichlorobenzene in an acylation reaction. You will probably need to do a generic search. 
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Offline Stri

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Re: Friedel-Crafts Acylation of Dihalobenzenes?
« Reply #3 on: April 09, 2010, 09:27:14 AM »
Orgopete, thank you for the response. I think I will request a literature example from my professor. I did attempt to find something before posting here, but I was unable to do so. If anyone can find an example, it would be much appreciated.

Thanks again!

Offline pacifyer

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Re: Friedel-Crafts Acylation of Dihalobenzenes?
« Reply #4 on: April 10, 2010, 05:38:53 PM »
The F-C ALKYLATION, will not work, but acylation certainly will.

Offline orgopete

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Re: Friedel-Crafts Acylation of Dihalobenzenes?
« Reply #5 on: April 11, 2010, 12:48:19 AM »
The F-C ALKYLATION, will not work, but acylation certainly will.

Could you please give a literature citation of an example?
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