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Author: Subject: Ridiculously easy alkali organometallic synth? (Benzyllithium)
palladium8
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[*] posted on 26-11-2014 at 22:07
Ridiculously easy alkali organometallic synth? (Benzyllithium)


According to patent US20060170118, full text, benzyllithium, benzylsodium, and benzylpotassium can be made by mixing the alkali hydroxide (e.g., NaOH) with toluene in DMSO and then evaporating off the DMSO and the formed water under vacuum. Yes, it says it can get solid benzyllithium, which is pyrophoric and highly energetic, out of hydroxide and toluene. Normally you make benzyllithium from n-butyllithium and toluene. The butyllithium (pKa=50) is a pyrophoric superbase, not LiOH, so that makes perfect sense.

The theory is that it's just an acid/base rxn with NaOH abstracting the PhCH2-H proton and leaving PhCH2Na plus H2O. This is only possible because supposedly toluene is more acidic than water when in DMSO.

PhCH3 + NaOH <--> NaPhCH2 + H2O (in DMSO)

Quote:
One tenth mole of toluene (9.2 grams) is dissolved in 100 ccs of DMSO at 25C under an inert atmosphere of argon. One tenth mole of lithium hydroxide is added to form one tenth mole of benzyllithium (11.4 grams) and one tenth mole of water (1.8 grams). The water and DMSO are removed under reduced pressure (10 mm Hg) leaving the solid benzyllithium which is best stored in hexane.


The patent states: "In DMSO, the pKa of toluene is 28.3 and the pKa of water is 29.2", which would seem to justify the idea as forming the allegedly weaker acid H2O would drive the reaction. However, I checked several pKa tables to find out that the claim is basically bullshit. The pKa of toluene in DMSO (under "Hydrocarbons") is 43, and the pKa of water in DMSO is 31.4 (under "Inorganic Acids"). :( I would think it's more likely that dimsyl sodium would form long before benzylsodium would.

How could the inventor just outright make up false claims? He said he was able to make some special polymer out of his organometallics, implying that the product was actually good enough to be used in further rxns. Maybe DMSO as the solvent is just to throw people off, and there's actually some other solvent that actually possesses the suitable qualities! :D I don't think a couple falsehoods can invalidate a patent. The motive is to keep people from copying without paying royalties. The patent was written generally in that it called for a "solvent that makes PhCH3 more acidic than H2O" and left DMSO just as an example. I've searched around papers and still haven't found a solvent in which toluene has a lower pKa than water, so if anyone knows, some or any kind of hint would be much appreciated, even by PM.

It wouldn't be difficult to actually test the procedure as written. Whether the solid at the end ignites in air is sufficient analysis. A few issues though:

- NaOH has low solubility in DMSO (<1g/L). So the NaOH will need to be powdered in a mortar and pestle, or better yet, ball milled for a few days. The reaction mixture will have to be under vortex stirring always because it's just going to be a suspension. The fact that NaOH isn't soluble in DMSO is another clue that DMSO isn't it

- The inert gas can just be a balloon of N2 or propane, even better.

- A new balloon of inert gas should be put on the flask right after vacuum. Then add hexane from a pressure equalizing funnel if the benzylsodium is to be stored, or the solvent for your new rxn.

If this can be gotten to work, then we have the easiest way ever of making this highly useful product. Benzyllithium or sodium can create C-C bonds to ketones and esters, for example. It can act like the umpolung of benzaldehyde--just make the other thing an aldehyde instead of a nucleophile. Lots and lots of possibilities. So what's the solvent?

Thanks for reading. Please offer suggestions.

[Edited on 27-11-2014 by palladium8]
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[*] posted on 26-11-2014 at 23:29


I don't understand the need for the whole hoo-ha about toluene being more acidic than H2O in a particular solvent, in this case DMSO. Assuming this works, then I would interpret this as Le Chaterlier's principle in action... a reaction with otherwise unfavourable equilibrium is pulled to the right by extracting H2O in high vacuum. The relative volatility between H2O and DMSO is probably huge at 25C.


UPDATE: I have calculated the relative volatility of water to DMSO @25C to be 39.5!

This is huge... as relative volatilities go and no surprise off course, but just wanted to pin a number to it.

[Edited on 27-11-2014 by deltaH]




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[*] posted on 26-11-2014 at 23:40


Makes sense.
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[*] posted on 26-11-2014 at 23:58


deltaH, thank you, that But I don't get how water would form in the first place if NaOH isn't basic enough to deprotonate toluene? Isn't there a huge energy barrier?

I guess the reaction wouldn't really be complete until all the water is gone, because PhCH2Na would quickly turn the water back to hydroxide. So water has to evaporate as it's formed; the "rate" would depend on the vacuum. The vacuum would need to be on the whole time.
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[*] posted on 27-11-2014 at 00:45


Yes, I take it the vacuum would indeed need to be on the whole time and this would probably take some time to go to completion... couple of days? Unfortunately, the inventor doesn't report the time taken in the example for complete evaporation.

As for the energy barrier, since I don't know what the activation energy for this reaction is, I couldn't say.

Bottom line, I think this reaction needs to be tried!

[Edited on 27-11-2014 by deltaH]




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[*] posted on 27-11-2014 at 12:37


Quote: Originally posted by j_sum1  
Makes sense.

I assume you are mocking on a mock patent application.




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[*] posted on 27-11-2014 at 16:48


My comment was on deltaH's consideration of equilibrium.

No intention of mocking anyone.

Quote: Originally posted by deltaH  


Bottom line, I think this reaction needs to be tried!


This looks a bit like the potassium sticky -- a patent for a straightforward procedure that seems to good to be true. The first few pages of that one make interesting reading as various people ironed out the bumps and eventually got it to work.
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[*] posted on 28-11-2014 at 08:41


Quote: Originally posted by j_sum1  
This looks a bit like the potassium sticky -- a patent for a straightforward procedure that seems to good to be true. The first few pages of that one make interesting reading as various people ironed out the bumps and eventually got it to work.

There is no such comparison at all. First of all, the potassium from magnesium patent never had the ambitions of being a mock patent. The possibility of it being truthful was based on solid thermodynamic data, while the possibility of this other patent application is being made completely and utterly impossible by the thermodynamic data. The mere idea that such a basic compound can be prepared and exist in a solvent that is approximately 100 million times more acidic than toluene is surrealistic. Why would toluene (bp 111 °C) evaporate more slowly than DMSO (bp 189 °C)? Why would BnLi/Na/K be stable in a solvent that is so acidic?

This patent application is still not a patent even though it was filed almost ten years ago. Apparently the USPTO patent examiners are not very keen to approve claims in mock patent applications. The application lists a single inventor who published 4 other patent applications of similarly mocking nature, yet did not bother to publish any of his breakthrough inventions in the scientific literature. Maybe he lives in a parallel universe where the laws of thermodynamics are written differently. Or maybe he just have a peculiar sense of humour, you know, like the trolls we encounter here.




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[*] posted on 28-11-2014 at 10:38


I recall reading that dimsyl sodium can be prepared (and reacted in situ) with DMSO/KOH. I suppose it could be classed as an "organometallic" compound -- which is nevertheless very easy to prepare. I could find the paper if there is a specific interest. It is referenced in one of the Gaylord bulletins, which I looked up. The use of alkoxides seems a more generally useful way to prepare it, though.


[Edited on 28-11-2014 by forgottenpassword]
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[*] posted on 28-11-2014 at 10:47


Makes more sense, nicodem ;)

Any chance that what he isolated were in fact methylsulfinylmethanide salts then? That might, nevertheless, be useful...

I wish there was a way to contact the inventor and ask him about it. This kind of patent is there to make money by licensing someone to produce it or provide you protection while you make money producing it yourself. Neither of these are possible if it doesn't work... just plain baffling why to bother with it.

There is a corresponding address for the inventor, but I could not find a contact number listed. Maybe someone else might have more luck and could ring him up.

EDIT: Snap forgottenpassword... I too just read about it in that same bulletin and wrote this as you posted, lol!

The technical bulletin I was reading was the one attached.

Attachment: DMSO technical bulletin.pdf (2.9MB)
This file has been downloaded 1682 times

[Edited on 28-11-2014 by deltaH]




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[*] posted on 28-11-2014 at 10:55


The dimsyl sodium is formed in tiny amounts. If it is used up in a reaction it can be synthetically useful; but simply distilling the DMSO off gives (I guess) just the base that was added. I read the KOH paper quite a while ago, but I was more interested in reactions with esters at the time to give b-ketosulfoxides, so I didn't consider using KOH. It's a good reaction to prepare b-ketosulfoxides. Yields are high. You just add a bit of sodium ethoxide to a DMSO solution of an ester. It's a good method for ester --> ketone conversions (with subsequent reduction of the sulfoxide with Zn/HCl).

[Edited on 28-11-2014 by forgottenpassword]
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[*] posted on 28-11-2014 at 10:56


Well, maybe not if the H2O evaporates off first, as I suggested above... it is after all a heck of a lot more volatile than the DMSO, but then again, that equilibrium would really not be favourable... still... it is enticing :D

[Edited on 28-11-2014 by deltaH]




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[*] posted on 28-11-2014 at 11:08


Quote: Originally posted by forgottenpassword  
I recall reading that dimsyl sodium can be prepared (and reacted in situ) with DMSO/KOH. I suppose it could be classed as an "organometallic" compound -- which is nevertheless very easy to prepare. I could find the paper if there is a specific interest. It is referenced in one of the Gaylord bulletins, which I looked up. The use of alkoxides seems a more generally useful way to prepare it, though.

No, sodium hydride is the reagent commonly used to prepare a solution of sodium dimsyl in DMSO. Supposedly sodium metal also works, but is obviously not practical.
Alkali hydroxides or alkoxides will not do. The pKa of H2O in DMSO is 31.4, while DMSO in DMSO has a pKa of 35.1. As one would expect, MeOH is more than 100 times more acidic in DMSO than water (pKa 29). Even t-BuOH in DMSO is not even ten times less acidic than water (pKa 32.2, compare that to its aq. acidity!). This means that even t-BuOK would only give an equilibrium amount of potassium dimsyl, but would not give full conversion. But making alkali dimsyl from alkali hydroxides or alkoxides by removing water or alcohols correspondingly at least does not sound as nonsense. While making benzylalkalis from alkali hydroxides makes just as much sense as it appears to make sense.




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[*] posted on 28-11-2014 at 11:22


I was tempted to think of this as a simple case of mistaken identity, but then what about example 4 in the patent and the claimed formation of the polymer and sodium chloride upon strong heating of the isolated product of the base, DMSO and p-chlorotoluene?

That would have to have been an outright lie if these were methylsufinylmethanide salts... again... I really want to believe that this guy wouldn't lie like that.

[Edited on 28-11-2014 by deltaH]




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[*] posted on 28-11-2014 at 11:23


Quote: Originally posted by Nicodem  
Quote: Originally posted by forgottenpassword  
I recall reading that dimsyl sodium can be prepared (and reacted in situ) with DMSO/KOH. I suppose it could be classed as an "organometallic" compound -- which is nevertheless very easy to prepare. I could find the paper if there is a specific interest. It is referenced in one of the Gaylord bulletins, which I looked up. The use of alkoxides seems a more generally useful way to prepare it, though.

No, sodium hydride is the reagent commonly used to prepare a solution of sodium dimsyl in DMSO. Supposedly sodium metal also works, but is obviously not practical.
Alkali hydroxides or alkoxides will not do. The pKa of H2O in DMSO is 31.4, while DMSO in DMSO has a pKa of 35.1. As one would expect, MeOH is more than 100 times more acidic in DMSO than water (pKa 29). Even t-BuOH in DMSO is not even ten times less acidic than water (pKa 32.2, compare that to its aq. acidity!). This means that even t-BuOK would only give an equilibrium amount of potassium dimsyl, but would not give full conversion. But making alkali dimsyl from alkali hydroxides or alkoxides by removing water or alcohols correspondingly at least does not sound as nonsense. While making benzylalkalis from alkali hydroxides makes just as much sense as it appears to make sense.


Well, yes -- ok. I was talking in terms of what would be useful to handle/use at home in my shed, rather than what is done in a properly equipped lab! The alkoxide method of producing it in situ is a useful one, though -- as mentioned above. I have lots of references with good yields of b-ketosulfoxides from in-situ reaction with esters; though I never actually did the reaction.

[Edited on 28-11-2014 by forgottenpassword]
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[*] posted on 28-11-2014 at 11:42


Quote: Originally posted by forgottenpassword  
The alkoxide method of producing it in situ is a useful one, though -- as mentioned above. I have lots of references with good yields of b-ketosulfoxides from in-situ reaction with esters; though I never actually did the reaction.

Just because alkali alkoxides can catalyse the Claisen condensations of esters with DMSO, it does not mean that they can also be used to prepare the alkali dimsyl. You are making huge leaps of reasoning. See the mechanism of the Claisen condensation to understand why. Actually, given that NaOH and KOH are nearly insoluble in DMSO, they too could potentially give some beta-ketosulfoxides even though they can hydrolyse esters. Yet, this again is no evidence that they can be used to prepare alkali dimsyls. It is only evidence that there is an equilibrium with useful concentrations of the reactive dimsyl anions. There is a huge leap from tiny equilibrium amounts of reactive species to a preparative level of conversion.




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[*] posted on 28-11-2014 at 11:57


I'm not claiming that they can be used to prepare the alkali dimsyl. In fact I explicitly suggested the opposite:
Quote: Originally posted by forgottenpassword  
The dimsyl sodium is formed in tiny amounts. If it is used up in a reaction it can be synthetically useful; but simply distilling the DMSO off gives (I guess) just the base that was added.

Anyway, nevermind -- we're at cross-purposes.
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[*] posted on 28-11-2014 at 12:53


Really tried to track down this mister Christian Everett, but without any luck. I wanted him to provide a little more details about his experiments. Sadly, this guy is a virtual ghost. He does have a basic LinkedIn profile though... but only the cursory type, doesn't say anything beyond his name and that he is a 'chemical professional'

My guess is that he's been retired for some time...

[Edited on 28-11-2014 by deltaH]




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[*] posted on 28-11-2014 at 18:51


The document cited as the source material for this thread is a patent application, not a patent. It is doubtful that this application will ever issue as a patent since there is no information presented that the methods described in the application actually produce the claimed products - no spectral evidence or further use of the claimed reaction products to provide new products that would be easily interpreted by one skilled in the art as arising from the claimed alkyl metal agents. Perhaps such data will be presented in an amended application at some later date but that is doubtful. By and large this application is at best speculative but most likely will be regarded as crap. Let it go.

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[*] posted on 28-11-2014 at 23:35


Quote:
By and large this application is at best speculative but most likely will be regarded as crap. Let it go.

I agree completely. I like to give people the benefit of the doubt, but this inventor has provided extremely little to go on. While initially I thought that perhaps this be exploiting favorable phase equilibria, nicodem rightly pointed out the volatility of toluene, which I completely and mistakenly overlooked, and negates any such advantage completely. While by the inventor's questionable reasoning, this wouldn't matter because he seems to imply the product forms immediately because of the ?!higher acidity of toluene in DMSO?!... literature suggests otherwise. So yeah... letting it go.




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[*] posted on 29-11-2014 at 01:47


I tried the procedure, though a little sloppily, and only got sodium hydroxide back at the end. Will give it one more go with argon and KOH when I have nothing better to do. I would think that if this is legit, then someone would have figured it out (long before 2005) just by accidentally mixing these reagents since there's so common.

Nicodem thanks for the insight.

I also tried e-stalking the author but couldn't find anything. If he really does R&D, he would be listed on some staff directory. Whatever his deal was, he gets props for his vivid imagination.
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[*] posted on 1-12-2014 at 13:28


I do remember from long ago that benzyl magnesium grignard and orthotolyl magnesium grignard reagents can interconvert to some degree due to the acidity of the toluene ortho proton being very close to the acidity of the benzylic protons on the toluene. I believe Francis Carey was the source of that knowledge, but can't find the reference right off hand.
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[*] posted on 1-12-2014 at 17:55


Quote: Originally posted by forgottenpassword  
I could find the paper if there is a specific interest.

Please do find the paper and post it here or in refs "for chemrox"
I don't know what you mean by specific need but I'm looking for ways to make a cmpd with an aryl group attached under conditions that a Li reagent would be helpful.




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[*] posted on 1-12-2014 at 18:00


Quote: Originally posted by palladium8  

I also tried e-stalking the author but couldn't find anything. If he really does R&D, he would be listed on some staff directory.

If you have a method for searching every company's staff directory worldwide I'd sure like to be tutored on that! You sound like the kind of hackers they create in Hollywood!

Edit by Nicodem: Corrected the text frame error.

[Edited on 2/12/2014 by Nicodem]




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[*] posted on 2-12-2014 at 06:44


Here are a few references to a few papers on the topic. I heard it at a Carey lecture years ago on chemistry that did not behave as written in text books. I wish I had the slides from that, but I don't.

Abnormal Reactions of Benzylmagnesium Chloride. II. The Mechanism of the o-Tolyl Rearrangement
John R. Johnson
J. Am. Chem. Soc., 1933, 55 (7), pp 3029–3032
DOI: 10.1021/ja01334a073
Publication Date: July 1933

Factors governing the reaction of the benzyl Grignard reagent. III. Formation of ortho and para products in reactions with alkyl sulfates via triene intermediates
Robert A. Benkeser , Thomas E. Johnston , Wen-Hong Tong
J. Org. Chem., 1968, 33 (6), pp 2203–2206
DOI: 10.1021/jo01270a007
Publication Date: June 1968

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