essbee
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Friedel Crafts acylation
How effective is anhydrous zinc chloride as a FC condensing agent? Everyone seems to use AlCl3, but the literature says many other chlorides may also
be used.
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TheChemiKid
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IIRC, a paper stated that AlCl3.0H2O was the best catalyst, and after that was ZnCl2.0H2O
I cannot find the paper now, but if I find it I will upload it.
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Nicodem
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Thread Moved
8-3-2014 at 04:58 |
blogfast25
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Quote: Originally posted by TheChemiKid  | IIRC, a paper stated that AlCl3.0H2O was the best catalyst, and after that was ZnCl2.0H2O
I cannot find the paper now, but if I find it I will upload it. |
I'm no expert on FC but I think trying to frame an answer in terms 'better' and 'best' is probably nonsensical.
Various Lewis acids are likely to be more suitable for certain types of FC, others for other types. Generalising here won't do much good.
Perhaps your paper pertained to one specific reaction?
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TheChemiKid
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I think it was on the synthesis of Ethylbenzene.
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essbee
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I've determined that ZnCl2 is a 'good' catalyst for some FC acylations ( a whole day surfing.....) but the question now is, does zinc chloride
immediately form a rather strong Lewis acid/Lewis base complex with the ketone function in the same way that AlCl3 does, basically does ZnCl2 have
the advantage over AlCl3 in that it is not needed in stoichiometric+ amounts?
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AvBaeyer
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If you haven't already done so you should take a look at Organic Reactions, Vol 3 (in the forum library) to aquaint yourself with the Friedel-Crafts
reaction. The review is a bit dated but the fundamental information is still useful. Overall, the choice of catalyst depends on a variety of factors
based on careful cosideration of the alkylating or acylating agent and the substrate as well as the solvent to be used. For example, under the right
set of conditions, even something as mild as iodine can induce a Friedel-Crafts acylation [See, for example, JACS 70, 1647 (1948) and JACS 68, 2639
(1946)].
AvB
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essbee
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Yes, nothing useful in the library.
Anyone have references for the use of Zinc chloride?
[Edited on 9-3-2014 by essbee]
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macckone
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| Quote: Originally posted by essbee |
Yes, nothing useful in the library.
Anyone have references for the use of Zinc chloride?
[Edited on 9-3-2014 by essbee] |
You could try some experiments and give us results.
I am not sure what you have in mind but if ZnCl2
is better than AlCl3 for some reactions
the information would be useful to the rest of us.
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smaerd
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There are seriously dozens if not hundreds of references for friedel crafts acylations using different lewis acids. It's substrate dependent... Being
more specific would yield better results more than likely. AlCl3 is typically considered a 'stronger' lewis acid. Even bismuth oxychloride has been
used. Amongst dozens of others; silica sulfuric acid, FeCl3, TeCl4, triflates, catalysts neat, catalysts in ionic liquids, etc... Each one can be
advantageous depending on the substrate, target, and desired 'process' (perhaps a deplorable word for amateur science). It sounds like you are
thinking in terms of green chemical principles? In which case bismuth oxychloride and derivatives thereof sound promising to me, unless something new
has popped out recently.
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essbee
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Yes indeed....I will have a try, my ZnCl2 was anhydrous when I bought it............... some time ago, so I will get some fresh stuff and see if it is
effective in an few FC experiments.
My lack of info is generally regarding workup, I am hoping for a 'simple' one like that of FeCl3 ( no black goo etc. ), so I guess that is the real
quest of my trials.
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