TheChemiKid
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p-Terphenyl from p-dichlorobenzene and benzene
Could I use a modified version of the Friedel–Crafts alkylation to form p-Terphenyl from p-Dichlorobenzene and Benzene with Anhydrous Aluminum
Chloride?
My idea would be to use 1 mole of p-Dichlorobenzene, 2 moles of Benzene, and 2 equivalents of Anhydrous Aluminum Chloride. Is this possible? I have
never seen any literature like this.
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FireLion3
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I know one way it could be prepared is in a cross coupling reaction between a halobenzene and dihalobenzene, in which the halogens are different so
that the catalyst only activates one or the other and so that the activated substrate can only react what it is supposed to react with.
If your reaction could work, or the one above I just wrote about, there is always the inevitability of homo coupling side-products.
About your reaction, I imagine it may work at first, assuming the Aluminum Chloride could activate the dichlorobenzene, to which if not you would need
to use a different halogen. Even if it does work, I don't think it will be viable since your product is far more nucleophilic and conjugated than
benzene and will react much more quickly with the electrophilic halobenzene than with benzene itself.
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UnintentionalChaos
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Quote: Originally posted by TheChemiKid  | Could I use a modified version of the Friedel–Crafts alkylation to form p-Terphenyl from p-Dichlorobenzene and Benzene with Anhydrous Aluminum
Chloride?
My idea would be to use 1 mole of p-Dichlorobenzene, 2 moles of Benzene, and 2 equivalents of Anhydrous Aluminum Chloride. Is this possible? I have
never seen any literature like this. |
Nope. There's a reason you've never seen any literature like it. You can't do FC alkylations with aryl or vinyl halides. The resulting carbocation
would be far too unstable.
You are looking to do a cross coupling. Pd is best and it still won't do what you want with those reactants. If you used chlorobenzene and copper
powder, you might be able to manage an Ullman reaction. The yield is not great and you'd still have to sort the desired productout from biphenyl and
other sideproducts.
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TheChemiKid
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Thanks for the help guys, I am still relatively new to Org. chem, so everything helps.
Edit: Typo fixed
[Edited on 7-27-2014 by TheChemiKid]
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UnintentionalChaos
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I too, own a jar of p-dichlorobenzene that I have never used...
It's really pretty useless. It's resistant to any sort of electrophilic aromatic substitution because the chlorines are deactivating. Nitration
requires fuming nitric acid to get even a single nitro on. I'm not even sure if it's any good for grignards. And even then, what would you make with
para-substitution?
If monodechlorination was possible, I'd do that because chlorobenzene is a pain in the butt to make.
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subsecret
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Is Friedel-Crafts impossible in this case because of the benzene ring's pi cloud?
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