I searched and didn't find anything on this, so here goes: I've read about several Friedel-Crafts alkylations in Vogel's, and they all
seem to need a large quatity of benzene. In some procedures the Benzene is used in a 15x molar excess. However the reaction volumes were also kind
of small, so I was wondering if it was done on a 3 L volume could it be done with only 3-4X molar excess or less, because that seems like a lot of
benzene for a little bit of reactanct.Marvin - 6-12-2004 at 15:20
The idea behind the excess is that benzene is cheap and a large excess avoids polysubstituted products. The newly substituted compound may even be
strongly activated towards furthur substitution increasing the dilution needed.Tweenk - 7-12-2004 at 14:35
Also, benzene acts as a solvent. The high excess needed can be rather easily separated after the rxn is done. The separation is worth its effort
because all F-C alkylations call for dry benzene, which is laborious to make - the one from the store usually contains a few % water and some
thiophene.
If you want you can use lower excess benzene but then you will get a very crappy batch and have to separate several products, which is even more
laborious than making large portions of dry benzene.Mendeleev - 7-12-2004 at 19:07
Thanks, I might try a friedel crafts in a month or so. Also I suppose the aluminum chloride can be recovered after the reaction, then dried with
CaCl2 in a vacuum desiccator?
[Edited on 8-12-2004 by Mendeleev]guaguanco - 8-12-2004 at 13:23
Quote:
Originally posted by Mendeleev
Also I suppose the aluminum chloride can be recovered after the reaction, then dried with CaCl2 in a vacuum desiccator?
[Edited on 8-12-2004 by Mendeleev]
I'd be surprised if it was practical to recover the AlCl3. The stuff absorbs and clings to water like nobody's business.
friedel-crafts alkylation..or, alkanoylation
johnnyBbad - 17-12-2004 at 16:32
..apparently, there are limitations to using the friedel-crafts alkylation, for eg., in the synthesis of actephenone from the reaction of benzene with
acetyl chloride in the presence of a lewis acid as a catalyst (eg.-AlCl3).
Quote: "The above reaction is accompanied by 2 important side reactions, one is polyalkylation(more than one alkyl group attaches itself to the
[benzene] ring); the otheris carbocation rearrangement (the intermediatecarbocation rearranges and so a different product is formed). This leads to a
decrease in useful yield and a mixture of products which are difficult to separate."
Thus, apparently, friedel- crafts alkylations are rarely used in these kind of chemical synthesis.
however, there is a second reaction, also developed by friedel and crafts, which involves an electrophilic carbon species that does NOT rearrange, and
that also deactivates the (benzene) ring to prevent further substitution(polyalkylation). This is the friedel- crafts ALKANOYLATION process.
To view the details of this reaction, try going to: http://www.chm.bris.ac.uk/webprojects2001/presly/new_page_4....Marvin - 17-12-2004 at 17:45
There is a mistake on the page, the diagrams are in the wrong places. Production of acetophenone is an example of acylation, not alkylation. Both of
these are typically considered together when we talk about freidel-crafts reactions. Some good information on the page though.
The important thing in looking at why it doesnt rearange is that by having a C=O on the end you form a stable carbocation on that carbon only. It
doesnt wander to other carbons that would then attack the ring.johnnyBbad - 18-12-2004 at 01:43
thanks marvin, I had a feeling something didnt add up with the equations on the page..I had written a note on the first page (which I had printed a
couple of weeks ago..and which, incidentally, I didnt see and didnt remember when I wrote the above comment this morning)
My Note: "some of this might be dodgy!!?? alkylation of benzene + propylene -> (1-methyl ethyl benzene)..wot gives??" end of hand
note..it just goes to show, mistakes are rife on the net. ApologiesMason_Grand_ANNdrews - 12-8-2006 at 11:29
I have a comnent to the Friedel-Crafts Alkylation. How will that work in practice, benzene to acetophenone and how will calculated the chemicals by
weigth ?
I`ve a idea only. I hope it is not stupid.
Prepare a mix of 70 ml benzene and 34 g anhydrous aluminum chloride. To this 52 ml of acethyl chloride is dropped and stirred in. I don`t know the
reaction is rigorous and cooling is required. The mix is than heated above 81 °C to vaporize the remainder of benzene and acethyl chloride and the
acetophenone is than removed from the mix by distillation above 202 °C.
I guess the oxidation of phenol to acetophenone is a common method.not_important - 12-8-2006 at 21:17
Drying benzene for FC is actually fauirlty simple. Put slight more benzene than you want into the reaction flask. Slowly distill the benzene, a short
fractionating column can be useful when doing this. Watch the distillate, sometimes it is helpful to catch a few drops in a test tube. So long as
there is much water in the benzene the azeotrope distills and the distillate will appear milky and/or drops of water can be seen in the benzene. Once
the distillate is a single phase, clear with not water drops in it, it's dry.
This also drys the flask, which can absorb a surprising amount of water especially for older flasks that have roughened surfaces.
Before doing that, thiophene is removed by shaking the benzene with medium concentrated H2SO4, I believe.
I'm sure you can find these mentioned in some of the books S.C. Wack has posted, the lab methods books from the 20s through the 50s have a lot of
useful information in them.
As for recovering the AlCl3, if you are doing an acylation the the AlCl3 is toast. It complexs with the carbonyl oxygen, the complex is destroyed in
the workup giving an aluminum salt or Al(OH)3.
On top of that it is difficult to remove water from hytrated AlCl3, it tends to lose HCl instead. Cheaper and easier to buy or make more via Al + dry
HCl or CL2.
For alkylations it is possible to recover the AlCl3, at least as a complex with the solvent, provided you can distill off the reaction product, the
AlCl3 can be reused with the next run of the same reaction. This really work best, for some values of 'best', with solvents such as nitrobenzene or
o-dichlorobenzene; YMMV.Sulfurman - 15-8-2006 at 03:45
benzene is not the only solvent you can use for Freidel Crafts alkylations: how about MeCl2, 1,2-dichlorobenzene or (maybe) Nitromethane?solo - 15-8-2006 at 06:44
There are recyclable catalysts that will save solvents and messy clean ups.......solo
-----------------------------------------------------------------------------------------------
Scandium(III) triflate immobilised in ionic liquids: a novel and recyclable catalytic system for Friedel–Crafts alkylation of aromatic
compounds with alkenes Choong Eui Song,*aWoo Ho Shim,bEun Joo Rohaand Jung Hoon Choi*b Chem. Commun., 2000, 1695–1696
Abstract
Scandium(III) triflate catalysed Friedel–Crafts alkylation of aromatic compounds with alkenes proceeded readily in the hydrophobic ionic liquid
solvents based on 1,3-dialkylimidazolium salts with easy catalyst/solvent recycling, whereas these reactions did not occur in common organic solvents,
water or hydrophilic ionic liquids at all.
Friedel crafts Reaction of three -Member Heterocycles II -Alkylation of Aromatic compounds with Aziridines Norman Milstein Journal of Heterocyclic Chemistry, pg.339, June 1968
Abstract
The Friedel Craft reaction of propylenimine with symmetrical arenes in the presence of aluminum chloride was investigated . Electron donating
substituents increase the alpha-methyl-beta-phenethylamine/beta-methyl-beta-phenethylaimine ratio, while increasing the temparature has the opposite
effect. In the reaction of chlorobenzene or toluene with aziridine , the nature of the substituent has little effect on the ortho/para ratio.
Note
This seems like a very interesting method and by using the method for synthesis of Benzene, that can be found here at sciencemadness, this looks
like a nice OTC method to an amine which can be improved by methylation.... although not familiar with Propylenimine and reading some of the
properties I wonder if anyone has had experience with this synthesis and if there are any down side to the procedure.............solo
Chemical and Use Information
Chemical Abstract Symbol (CAS)
75-55-8
Additional CAS Numbers
None
Use Information
Propyleneimine is used as a chemical intermediate in the modification of latex surface coating resins, polymers in textile and paper industries, dyes,
photography, gelatins, oil additives and organic synthesis. It is a comonomer for polymers with methacrylic acid and esters.
Propyleneimine can be made from treating alaninol hydrogen sulfate(1), monoisopropanolamine hydrogen sulfate(2), 2-bromopropylamine(3) or
2-chloropropylamine(4) with NaOH.
(1)
J. Am. Chem. Soc. 81 (1959) 4689,4690.
J. Am. Chem. Soc. 104, 26 (1982) 7573-7580.
(2)
Chem. Lett. (1982) 1479-1480.
(3)
Chem. Ber. 50 (1917) 823.
(4)
J. Am. Chem. Soc. 81 (1959) 4689,4690.
Take note that propyleneimine is ranked as one of the most hazardous compounds (worst 10%) to ecosystems and human health.
It is very toxic and a known carcinogen.
Also I checked Acros and Alfa catalogs and they don't seem to carry it...
