Sciencemadness Discussion Board

Possible Path to Tetraphenylmethane

ssdd - 24-1-2008 at 20:37

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]

Gomberg syn

chemrox - 24-1-2008 at 22:12

The Gomberg synthesis of this compound is outlined in Wiki:

http://en.wikipedia.org/wiki/Tetraphenylmethane

not_important - 24-1-2008 at 22:39

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.

JohnWW - 25-1-2008 at 01:58

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.

ssdd - 25-1-2008 at 06:58

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]

ssdd - 29-1-2008 at 16:45

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

Nicodem - 30-1-2008 at 02:01

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.

garage chemist - 30-1-2008 at 02:06

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.

Gomberg Synth Question

ssdd - 23-9-2008 at 12:34

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

Nicodem - 23-9-2008 at 13:58

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 396 times

ssdd - 23-9-2008 at 14:17

Thank you very very much for the references.

-ssdd

ssdd - 23-9-2008 at 17:36

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

not_important - 23-9-2008 at 18:58

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.