[Stri]

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

[sHaY]

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.

[orgopete]

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. 

[Stri]

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!

[pacifyer]

The F-C ALKYLATION, will not work, but acylation certainly will.

[orgopete]

The F-C ALKYLATION, will not work, but acylation certainly will.

Could you please give a literature citation of an example?