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Author: Subject: Friedel Crafts with Al-amalgam
bio2
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[*] posted on 15-5-2006 at 01:40
Friedel Crafts with Al-amalgam


Note that this is a catalytic amount!

Does anyone know of other substrates that work with this type prodedure.? 2- Chlorobutanone for example?

120g Bz + 60gPhMeCl + 2g Al --> 35g Ph2Me

NOTE.—In the preparation of certain compounds by condensation as the result of the elimination of chlorine and hydrogen, an aluminium-mercury couple gives better results than aluminium chloride. It is probable that a little aluminium chloride is first formed by the action of the metal on the
organic halogen compound; the presence of mercury makes the aluminium more active.
..............................................
166. Preparation of Diphenylmethane (SECTION 435).—As a
large amount of hydrochloric acid is formed in the preparation
the apparatus should be set up under a hood. In a 500-cc. flask
provided with a reflux condenser, place 120 grams of benzene
and an aluminium-mercury couple which is prepared as follows:
Cut up 2 grams of aluminium foil into strips about 1 inch by
0.5 inch and allow them to stay in a solution of mercuric chloride,mad by dissolving 1 gram of the salt in 200 cc. of water, for 8 to 10 minutes; a film of mercury is deposited on the aluminium. Wash the couple thoroughly with water, then with alcohol, ether, and finally with benzene. Into the upper end of the condenser place a separatory funnel containing 60 grams of benzyl chloride; allow the chloride to drop very slowly into the flask. At the end of n hour heat the flask on a water-bath for about 15 minutes. Pour the contents of the flask into an equal volume of water,which contains a little sodium hydroxide, shake, separate the benzene solution, and extract the aqueous layer once with a little benzene. Combine the benzene solutions, and dry them with calcium chloride. Pour off the solution into a distilling flask, and distil, using a condenser, until the temperature of the vapor reaches 150°. Remove the condenser, attach a short air condenser, distil, and collect the fraction which boils at 250°-300°. Redistil and collect the portion boiling at 255°-265°. Record the weight obtained, and calculate the percentage yield from the benzyl chloride. The yield should be about 35 grams. Diphenylmethane melts at 26° and boils at 262°.


EbChem.: Spelling of title

[Edited on 16-5-2006 by chemoleo]
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[*] posted on 15-5-2006 at 09:53


IIRC you need a full stoichiometric quantity of the AlCl3 to get acid chlorides to react with benzene because the ketone that is formed produces a complex with the AlCl3.
If the substrate is a ketone to begin with I think you will run into problems.
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[*] posted on 15-5-2006 at 12:34


the friedel-crafts calls for acid halides. PhMeCl isn't an acid halide, so this shouldn't work. PhCOCl, followed by reduction of the formed carbonyl would work.



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[*] posted on 15-5-2006 at 15:14


This is the source reference which I neglected to post.

EXPERIMENTAL ORGANIC CHEMISTRY

BY JAMES F. NORRIS
Professor of Organic Chemistry, Massachusetts Institute of Technology; Author of "The Principles of Organic Chemistry," "A Textbook of Inorganic Chemistry for Colleges," and Joint Author of "Laboratory
Exercises in Inorganic Chemistry"

SECOND EDITION

McGRAW-HILL BOOK COMPANY, INC.
NEW YORK: 370 SEVENTH AVENUE
LONDON: 6 & 8 BOUVERIE ST., E. C. 4
1924


...............IIRC you need a full stoichiometric quantity of the AlCl3 to get acid chlorides to react with benzene because the ketone that is formed produces a complex with the AlCl3......

This is the conventional F&C which can also be done with other Lewis acids and in different ways of which this is one I quess.

.......If the substrate is a ketone to begin with I think you will run into problems.........

Yes, my thoughts as well and benzyl chloride is much more reactive than
most other substrates however if this works it would be incredibly useful
compared to handling large amounts of anhydrous AlCl3. Anyone who has handled more than a few grams of the stuff can attest to that.

.....the friedel-crafts calls for acid halides. PhMeCl isn't an acid halide, so this shouldn't work.......

Yes, in the conventional wisdom yet the F&C mechanism has been more broadly applied. I don't think Professor Norris would be very pleased to find out that his procedure doesn't work anymore, lol. Perhaps under a different name.

At any rate this method seems very elegant to me and the key is in this statement:

"In the preparation of certain compounds by condensation as the result of the elimination of chlorine and hydrogen, an aluminium-mercury couple gives better results than aluminium chloride."

So these certain compounds are being researched as applies to this method which is a new one to me. If .5% Al Amalgam will do as stated then this is revolutionary even today, never minding 1924.
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[*] posted on 16-5-2006 at 11:05


I have seen both the alkylation and the acylation refered to as F-C reactions. To be honest, I have't checked if Drs F and C used both, and I don't care
For the alkylation you can use a catalytic amount of the Lewis acid. If you are careful you can also cheat and use a little AlCl 3 and rather more Al. As the reaction proceds it forms HCl which converts the Al to yet more catalyst. Since this is an exothermic reaction that generates lots of a corrosive toxic gas, setting it running under autocatalytic conditions is rather risky. This procedure looks like a variation on this theme.
It won't work with the haloketone you sugest, partly because the AlCl3 will react directly with the ketone. Partly because under strongly acid conditions the ketone will react with itself and partly, I suspect, because the metal will do vaguely pinacol-reaction like things to the ketone.
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[*] posted on 16-5-2006 at 16:50


From the Encylcopedia of Reagents for Organic Synthesis:

Friedel-Crafts Alkylation catalyst. Aluminum catalyzes orthoalkylation of anilines and phenols with alkenes. Preformed aluminum anilides or phenoxides exhibit susceptibility toward alkene attack and usually o,o'-dialkylated products predominate. Selective ortho-alkylation of phenol can be accomplished using aluminum soft drink cans as the reagent.

Laan & Ward Chem Ind (Lon) 34 (1987)
Stroh, Eberberger, Haberland & Hahn Angew Chem 69 124 (1957)
Ecke, Napalitano, Filbey & Kolka JOC 22 639 (1957)


:D

[Edited on 17-5-2006 by leu]




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[*] posted on 17-5-2006 at 03:26


Beer can Al alloy isn't so pure, wonder what the secret is?
Shitty yields maybe.

Found this same reaction in OS.

This excerpt caught my attention as only about 9mole%
Al to PhMeCl is used!

........Succeeding batches may be started in the same flask containing the aluminum turnings and the trace of tarry material without the addition of further catalyst; these batches do not show an induction period.............

....Organic Syntheses, Coll. Vol. 2, p.232 (1943); Vol. 14, p.34 (1934).
DIPHENYLMETHANE
[Methane, diphenyl-]
Submitted by W. W. Hartman and Ross Phillips.
Checked by Reynold C. Fuson and S. H. Babcock.
1. Procedure
In a 5-l. flask, provided with a reflux condenser and an S-tube attached to a dropping funnel, are placed 2 kg. (2.3 l., 25.6 moles) of benzene, which has been dried by distilling until the distillate comes over clear, and 10 g. of amalgamated aluminum turnings (Note 1). The benzene is heated to boiling on a steam bath, the steam is turned off, and 500 g. (3.96 moles) of benzyl chloride is added at such a rate as to cause the solution to boil (Note 2). The hydrogen chloride is absorbed in water or allowed to pass out-of-doors. When all the benzyl chloride has been added (one hour), the mixture is warmed for ten to fifteen minutes, or until the evolution of hydrogen chloride ceases. When cool, the benzene solution of diphenylmethane is decanted from the small amount of tarry material (Note 3) and washed with 5 per cent sodium hydroxide solution and then with water. After a partial drying with calcium chloride, the benzene is distilled from a steam bath and the residue fractionated under diminished pressure. The fore-run is collected up to 125°/10 mm., the main product at 125–130°/10 mm., and an after-run up to 150°/10 mm. (Note 4). Redistillation of the fore-run and after-run yields a small amount of material which is added to the main fraction. The latter is chilled and a small amount of oil is decanted from the crystals. The yield of material melting at 24–25° is 330–350 g. (49.5–52.5 per cent of the theoretical amount).
2. Notes
1. Amalgamated aluminum is prepared as follows: Aluminum turnings, freed from any oil by washing with ether, are stirred with a 5 per cent mercuric chloride solution for a few minutes and then washed quickly with water followed by methyl alcohol. The amalgamated aluminum is used at once.
2. At times the reaction is slow in starting. Not more than 50–60 g. of benzyl chloride is added at first, and the mixture is heated until the evolution of hydrochloric acid indicates that the reaction is under way. If too much benzyl chloride is present when the reaction starts, the contents of the flask may boil over.
3. Succeeding batches may be started in the same flask containing the aluminum turnings and the trace of tarry material without the addition of further catalyst; these batches do not show an induction period.
4. The material in the residue and high-boiling fraction may be partially converted into diphenylmethane by heating with one-third its weight of aluminum chloride and five times its weight of benzene.
3. Discussion
Diphenylmethane can be prepared from benzene and benzyl chloride with aluminum chloride,1 hydrogen fluoride,2 beryllium chloride,3 the double salt of aluminum and sodium chlorides,4 zinc dust,5 zinc chloride,6 or aluminum amalgam7 as a condensing agent. The procedure described above is a slight modification of the last method.
Benzene and benzyl alcohol furnish diphenylmethane on treatment with boron fluoride,8 hydrogen fluoride,9 or beryllium chloride.3 Diphenylmethane has also been prepared from benzene, methylene chloride, and aluminum chloride,10 and from benzene, formaldehyde, ethanol, and concentrated sulfuric acid.11 The reduction of benzophenone to diphenylmethane has been effected by hydriodic acid and phosphorus,12 sodium and alcohol,13 and fusion with zinc chloride and sodium chloride.14 The condensation of benzylmagnesium chloride and benzene to diphenylmethane can be brought about by small amounts of magnesium and water.15........
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[*] posted on 18-5-2006 at 18:16


It is not necessary to prepare amalgam of Al; directly adding small pieces of foil of Al at the reagents
and soon to add a little anhydrous HgCl2 causes that the reaction begins quickly (exothermic and must be moderated with cooling) this way I have obtained cumene of
benzene and isopropyl chloride and also other reactions
between an aromatic hydrocarbon and a halogenous derivative
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[*] posted on 19-5-2006 at 01:56


...It is not necessary to prepare amalgam of Al; .........

By this you mean separately I quess. The method you
mentioned forms the amalgam in-situ.

How much Al do you use? expressed as mole% or weight %
of total reactants?

......halogenous derivative.........

Preferably a hydrocarbon? Do some of the other
standard halogenated F&C reagents condensed with benzene also
work with activated Al in lieu AlCl3?

[Edited on 19-5-2006 by bio2]
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[*] posted on 19-5-2006 at 16:10


Indeed takes place ¨in situ¨ Aluminum amalgam and
AlCl3 that acts catalytically being enough a smaller amount
to 1g In the preparation of cumene I used a ratio 2:1
(benzene/isopropyl chloride) with a approximate yield
to 50% of cumene; of course using greater excess of benzene it must obtain better yields. Other reactions done as a test and that quickly they happen for example:
* toluene in excess + CHCl3
* toluene + CH2Cl2
* only verification of the reaction without isolating products
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