Quote: Originally posted by kuro96inlaila | Quote: Originally posted by CuReUS | the problem with FC alkylation of acetophenone is that the AlCl3 reacts with the ketone group rather than with alkyl halide to form the
electrophile.The problem can be overcome by using an excess of AlCl3 |
How did the excess of AlCl3 prevent the formation of ketone electrophile? |
I had a feeling my sentence about the electrophile would cause a confusion.I am sorry
what I meant was that the instead of reacting with the alkyl halide and forming an electrophile(like a normal FC reation) , the AlCl3 would
form an adduct with the ketone group.
Now suppose you are using 1 mole of acetophenone and you put in 2 moles of AlCl3(which is an excess), I mole of AlCl3 gets
wasted reacting with the ketone,but the remaining 1 mole reacts with the alkyl halide to form the eletrophile which attacks the benzene ring.
Quote: | alkylation by alcohol and H2SO4 probably can be done on acetophenone too consdering -NO2 is a strong deactivating
group compared to ketone being moderate deactivating group. |
I was thinking the same thing too.But my only worry is that there might be an acid catalysed aldol reaction.
Quote: | Would FeCl3 be a more suitable catalyst than AlCl3? or would SbF5 sufficient for most FC reaction?
|
the only difference I know between FeCl3 and AlCl3 is that since the former is less reactive, it forms the carbocation(from the
alkyl halide) slowly because of which there is a lesser chance of rearrangement.For ex - suppose you react propyl bromide with benzene in the presence
of AlCl3, you will get isopropylbenzene but if you use FeCl3,you will get n-propylbenzene
SbF5 is a very strong lewis acid,so it should be sufficient for most FC reactions.
[Edited on 11-8-2016 by CuReUS] |