ssdd
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Possible Path to Tetraphenylmethane
So I am attempting a possible method to Tetraphenylmethane that if it works will prove that the method works for another compound I am trying to make.
Heres what I am thinking:
Triphenylmethanol to Triphenylmethyl Chloride
Using this run a Friedel-Crafts reaction with the Chloride under Benzene with AlCl3 as the catalyst.
This should produce Tetraphenylmethane and HCl.
1. Does this sound reasonable?
2. Is Triphenylmethanol soluble in Benzene? If not will this still work?
3. The product produced is highly insoluble and will not be soluble in Benzene (it is not even all that soluble in DMF), will the solid being formed
hinder the reaction as liquid levels become less and less?
4. Is the HCl produced a gas or dissolved in the solvent?
5. What is the best temperature for this reaction to be run at?
Thanks for any input you may have, I plan to give these reactions a run within the next two weeks,
-ssdd
[Edited on 24-1-2008 by ssdd]
All that glitters may not be gold, but at least it contains free electrons.
-- John Desmond Baernal
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chemrox
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Gomberg syn
The Gomberg synthesis of this compound is outlined in Wiki:
http://en.wikipedia.org/wiki/Tetraphenylmethane
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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not_important
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I don't believe it works.
The original preparation of tetraphenylmethane reacted trityl bromide with phenylhydrazine to get the disubstituted hydrazine, which was oxidised to
the azo compound. This was then heated to give tetraphenylmethane and N2.
see here
http://books.google.com/books?id=3NwBAAAAYAAJ&pg=RA1-PA7...
One route is the reaction of triphenylmethanol with aniline hydrochloride to give the substituted tetraphenylmethane, and remove the NH2 though the
diazo route.
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JohnWW
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Tetraphenylmethane is hard to prepare, because of severe steric strain; Moses Gomberg was the first chemist tp prepare it, in the 1890s, after several
other eminent chemists failed. He tried to prepare the whole series of completely phenylated alkanes.
In 1900, Moses Gomberg also tried to prepare hexaphenylethane, by reaction of triphenylmethyl chloride or bromide with Zn dust. However, it was found
that what he got in the presence of atmospheric oxygen was triphenylmethyl peroxide. He thought that he finally had hexaphenylmethane when he did the
reaction in the absence of air, obtaining a white solid of the right composition; but even this was shown in 1968 to be (C6H5)3C-C6H5=C(C6H5)2, the
middle C6H5 having a quinonoid disposition of two double bonds. In the absence of air or other oxidants, this dissolved in hydrocarbon solvents to
give an intense yellow solution, which by ESR and depression of the freezing-point was confirmed to be the triphenylmethyl radical, (C6H5)3C , with
an unpaired electron which is resonance-delocalized over the whole molecule, conferrig stability although still very reactive.
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ssdd
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not_important, I am currently using the aniline hydrochloride method to try and produce the compound I am trying to make, as it works very well for
Tetraphenylmethane, it is much more difficult with the compound I am working on as there are about 20 compounds produced in the reaction. (Flourene
bonds are formed along with several other products) So, currently my group is searching for an alternative to this because we cant seem to purify the
compound we want out. (And the ways we are trying to purify e.g. column chromatography seem to be leading to yet more reactions.
Though the Gomberg synth sounds interesting and may be worth giving a run assuming the school has/will buy the reagents.
Thanks for your interest,
-ssdd
[Edited on 25-1-2008 by ssdd]
All that glitters may not be gold, but at least it contains free electrons.
-- John Desmond Baernal
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ssdd
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OK, so I proposed the reaction above (my original) to my professor, he feels that this has a shot in ____ at working.
So next week we will be running this starting with triphenylmethyl chloride which apparently the school has some of saving me a step in the reaction.
I will post back in a week with the results of this.
My Current Plan:
Dissolve .25g of triphenylmethyl chloride into enough benzene to dissolve it, then add a large excess of benzene to prevent side products.
This is all placed into a three neck flask with a condenser in the center and FeCl3 in a drying tube at the top to capture HCl gas produced. A
Nitrogen line runs into one of the necks to run this under a nitrogen atmosphere. And the last neck is stopper for the addition of additional
reactants.
Once the TPMC is dissolved in benzene AlCl3 is added until a reaction is observed. (This is shown by the production of HCl gas.) If the reaction
becomes to vigorous it will be cooled on a salt/ice bath. Once production of HCl stops the mix will be refluxed for 45min-1hour depending on time
limitations.
From this, hopefully, the AlCl3 can be filtered away and the product can be harvested from solution.
So far I think it sounds good, I'll let you know how it goes.
-ssdd
All that glitters may not be gold, but at least it contains free electrons.
-- John Desmond Baernal
http://deepnorth.info/ |
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Nicodem
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You got me confused here. Why, after you have been told that the Friedel-Crafts alkylation can not be used to prepare tetraphenylmethane from trityl
chloride and benzene, you still believe it would work? What are your (and your professor’s) arguments in not believing the published literature on
this issue? If Gomberg as well as others were unable to obtain tetraphenylmethane by such an alkylation, what kind of an innovation will you use in
order to force the reaction to yield tetraphenylmethane instead of the usual mixture of crap?
Also, why don’t you use one of the so many published methods? If you don’t like Gomberg’s radical coupling, why don’t you use the coupling of
PhMgX with trityl chloride? That’s a preparation for which there is at least a dozen of references and, though just as low yielding, is quite simple
given PhMgBr is commercially available.
…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!
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garage chemist
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I can say for sure that triphenylmethyl chloride and benzene w/AlCl3 will yield absolutely no tetraphenylmethane.
Reason: The well-known laboratory synthesis of triphenylmethyl chloride uses the reaction between carbon tetrachloride and an *excess* of benzene in
the presence of AlCl3. The reaction goes straight to triphenylmethyl chloride and then stops completely.
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ssdd
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Gomberg Synth Question
OK so I have in front of me a printed diagram from Gomberg's synthesis of tetraphenylmethane.
Outside of this diagram I can find almost no information as to carry out this reaction. Does anyone have any idea at all the procedure for running a
reaction similar to the first 3 steps of this reaction? http://upload.wikimedia.org/wikipedia/en/f/fd/Tetraphenylmet...
Thanks for any help,
-ssdd
All that glitters may not be gold, but at least it contains free electrons.
-- John Desmond Baernal
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Nicodem
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The obvious solution is to read the original publications and the references therein:
Tetraphenylmethane
Gomberg, M.
Berichte der Deutschen Chemischen Gesellschaft, 30 (1897) 2043-2047. (freely available at Gallica)
On tetraphenylmethane
M. Gomberg
J. Am. Chem. Soc., 20 (1898) 773-780. DOI: 10.1021/ja02072a009
Hydrazo- and azo-derivatives of triphenylmethane
M. Gomberg, A. Campbell
J. Am. Chem. Soc., 20 (1898) 780-789. DOI: 10.1021/ja02072a010
...and the review:
Tetraphenylmethane
Gomberg, M.; Kamm, O.
J. Am. Chem. Soc., 39 (1917), 2009-2015. DOI: 10.1021/ja02254a016
(the JACS papers are attached)
PS: The thread has been merged with the already existing one on the same subject.
Attachment: Gomberg.rar (1.2MB)
This file has been downloaded 315 times
…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!
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ssdd
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Thank you very very much for the references.
-ssdd
All that glitters may not be gold, but at least it contains free electrons.
-- John Desmond Baernal
http://deepnorth.info/ |
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ssdd
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Question:
I was reading the reference titled 'tetraphenylmethane' and I encountered a point of confusion. In this Gomberg suggests heating a reaction containing
ether to 120-140*. Knowing that ether has a very low boiling point I ask does anyone know if he is referring to Fahrenheit of Centigrade? While I know
it is common to use centigrade this article is very old... Or can anyone clear up why it would need heated so much just to distill off ether?
-ssdd
All that glitters may not be gold, but at least it contains free electrons.
-- John Desmond Baernal
http://deepnorth.info/ |
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not_important
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The Gomberg article clearly states that
| Quote: | | After the reaction was complete the excess of ether was distilled off by warming the mixture in an oil bath, the
temperature being gradually raised until the thermometer in the bath indicated 120 to 140. At this stage there was added, without cooling, 10 g. of
the ethyl ether of triphenylcarbinol. |
Even if that was confusing, as 120 F is above the boiling point of ether it should be clear from that fact that the reaction was not being carried out
in boiling ether unless it was under pressure.
U.S. publications were likely to be in Fahrenheit prior to some date, 1917 sounds a bit late for that to be true.
Given that, and that the next step emphasizes that the flask and its contents are not cooled before adding the next reactant, it should be clear that
the high end of heating is to react the desired reaction temperature rather than needed to remove ether.
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