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My text book says that halobenzenes can be prepared by aromatic substitution on benzene ring by using Fe or FeX3 as Lewis acid but this method isn't useful for preparation of fluoro benzene because of it's high reactivity.

My question is what will be the product if FeF3 is reacted with benzene, I tried searching a bit on internet but couldn't find anything helpful.

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    $\begingroup$ Halides are only catalysts in Friedel-Crafts halogenation. Without halogen there's no reaction. $\endgroup$
    – Mithoron
    Nov 2 '20 at 14:02
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    $\begingroup$ Ferric halides plus elemental halogen (Cl2, Br2) give the functional equivalent of Hal+. The functional equivalent of F+ cannot be made this way. $\endgroup$
    – Waylander
    Nov 2 '20 at 14:27
  • $\begingroup$ See: chemistry.stackexchange.com/questions/21604/… $\endgroup$ Nov 2 '20 at 15:10
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Iron catalyst will not be needed as Fluorine will react directly with benzene explosively, the probable product formed would be hexaflurocyclohexane , which can predicted by looking at similar reaction of chlorine with benzene in presence of UV rays which is mentioned in NCERT class 11 chemistry Textbook.

Replace Cl with F and and since fluorine is more reactive UV light is not needed.

(Replace $Cl$ with $F$ and since fluorine is more reactive UV light is not needed.)

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    $\begingroup$ With fluorine, depending on conditions, I wouldn't be surprised to find the product is carbon tetrafluoride (amongst other things) $\endgroup$
    – Ian Bush
    Nov 2 '20 at 14:26
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    $\begingroup$ I strongly suspect you would generate a complex mixture (and a great deal of heat) $\endgroup$
    – Waylander
    Nov 2 '20 at 14:28
  • $\begingroup$ It may be possible that a lot of products are formed but I tried to compare reaction with a similar known reaction so the predicted product can also be formed, maybe this type of question involves experiments too. $\endgroup$ Nov 2 '20 at 14:40
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    $\begingroup$ From what I remember of organic a general rule of thumb is the following reaction: organic + F2 -> mess + bang $\endgroup$
    – Ian Bush
    Nov 2 '20 at 15:07

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