FriedBrain
Harmless
Posts: 14
Registered: 10-8-2015
Location: Germany
Member Is Offline
Mood: No Mood
|
|
Friedel Crafts Alkylation of Pyrene, whats wrong?
Hey folks,
I wanted to make some 2,7-Di-tert-butylpyrene for further synthesis (with a friend of mine, maybe pictures coming  )and tried to prepare it today following this paper: http://dx.doi.org/10.1080/00397911.2010.517893
It says:
"To a mixture of 10 g of pyrene (1) and 100 ml of dichloromethane in a 250-ml, three-necked flask were added 650 mg of aluminum chloride and a
solution of 10 g of t-butylchloride in 15 ml of dichloromethane under a nitrogen atmosphere at 5 C."
I did as described with about a fitth of the amounts. After 4h of stirring at RT (as described) I made a TLC of the reaction mixture to see if it's
completed, but it seems like none of the t-butylpyrene is produced, since I can see only one spot (pretty strong) of the used pyrene (made a TLC of
the pyrene paralel).
I wonder why so little aluminiumchloride was used, since for a FC equivalent amounts(here it's just about 0.05eq!) should be used. I just throwed way
more AlCl3 in it for safety, and it gets darker so more AlCl3 is added (its kind of black now). I'll let it stir over night.
Does anyone know why it didn't form any product, was my last t-BuCl.. 
[Edited on 13-8-2015 by FriedBrain]
You always have time to do some chemistry, but maybe you just have other priorities?
|
|
|
AvBaeyer
National Hazard
Posts: 644
Registered: 25-2-2014
Location: CA
Member Is Offline
Mood: No Mood
|
|
Do you know that your tlc system can resolve the starting material and the product?
AvB
|
|
|
Waffles SS
Fighter
Posts: 998
Registered: 7-12-2009
Member Is Offline
|
|
Your Aluminium Chloride is anhydrous?
Use CCl4 instead of Dichloromethane(i had same problem when i used CH2Cl2 for every Friedel Crafts Alkylation or Acylation)
|
|
|
FriedBrain
Harmless
Posts: 14
Registered: 10-8-2015
Location: Germany
Member Is Offline
Mood: No Mood
|
|
Yes, my Aluminiumchloride was pretty anhydrous, since it smoked a little bit and wasn't clumpy. And the used solvent (Petrolether) should dissolve the
product too.
I let it react over night, after I added some more Aluminiumchloride and after a TLC it seems like the spot moves a little bit further then the
pyrene, maybe that's my product? I just filtered it off a silica gel pad and now I'm going to distill all the chloroform off, and well, hope that It's
my di-t-butylpyrene^^
Thanks for help though 
You always have time to do some chemistry, but maybe you just have other priorities?
|
|
|
Nicodem
Super Moderator
Posts: 4230
Registered: 28-12-2004
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by FriedBrain  | | I wonder why so little aluminiumchloride was used, since for a FC equivalent amounts(here it's just about 0.05eq!) should be used.
|
Friedel-Crafts alkylations require tiny amounts of the acid catalyst, essentially just a few mol% (that includes the amout that is quenched by
moisture). In fact, in the seminal work by Friedel and Crafts there was no acid used, they discovered the reaction by applying zinc powder which
provided tiny amounts of zinc halides in situ.
You are probably confusing this reaction with the Friedel-Crafts acylation which indeed commonly requires stoichiometric amounts of the acid, but that
is because the acid gets consumed in the reaction by forming a complex with the ketone product.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
