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Author: Subject: Orthosilicate esters from silica gel
Triflic Acid
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[*] posted on 18-5-2021 at 07:59
Orthosilicate esters from silica gel


I'm trying to make TEOS(tetraethyl-orthosilicate) for some experiments, but I don't like the normal Si --> SiCl4 --> Si(OEt)4 route. The two attached papers look promising. I'm leaning Cheng2000 paper, since it is slightly easier for me to replicate. Would reacting ethanol with the diethylene orthosilicate intermediate that they product create TEOS? Also, in the patent, how do they prevent the ethanol from boiling off?

Attachment: cheng2000.pdf (275kB)
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Attachment: US4288604.pdf (930kB)
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[Edited on 5-20-2021 by Texium]




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[*] posted on 19-5-2021 at 17:20


bump...



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[*] posted on 19-5-2021 at 21:27


Organosilicon compounds are organometallic compounds containing carbon–silicon bonds. not Si-O-C bonds.
if you to follow first PDF you need amorphous SiO2 like from rice hull ash or silica fume.Greener Silica From Rice




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[*] posted on 20-5-2021 at 06:48


I was thinking of using kitty litter silica gel, would that work? Also, sorry about the naming mistake, I'll try to change it to tetraalkyl orthosilicates.

[Edit: can a mod do that, I don't think I can]

[Edit2: Thanks Texium]

[Edited on 20-5-2021 by Triflic Acid]

[Edited on 20-5-2021 by Triflic Acid]




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[*] posted on 20-5-2021 at 09:12


maybe catalytic amounts of anhydrous Hydrogen fluoride or much more obtainable anhydrous Ammonium fluoride in anhydrous ethanol can be electrolyzed with Si anode and Ni cathode to make solution of Tetraethyl orthosilicate in anhydrous ethanol.(total hypothesis based on guesswork)



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[*] posted on 20-5-2021 at 09:14


Maybe, but I'm don't really like the idea of having to use HF, since then I can't use a glass system. And if I could deal with HF I would just make some SiF4 from SiO2 and go that way.

[Edited on 20-5-2021 by Triflic Acid]




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[*] posted on 20-5-2021 at 09:35


Ammonium fluoride is much safer and i think tiny bit should work just to dissolve SiO2 layer on Si and also make the solution conductive. just use plastic and i think you can't make orthosilicates with SiF4 gas, too stable to react with alcohols, maybe with alkoxides. SiF4 is made at room with SiO2 with HF and with more HF to H2SiF6.



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[*] posted on 20-5-2021 at 09:43


But, assuming that I decide to stick to the first paper(Cheng2000) I posted, since I don't have ammonium fluoride at hand. Could I make tetraethyl orthosilicate by reacting the diethylene orthosilicate with ethanol. It seems like it should work, since ethylene glycol is a better leaving group than ethanol. I kind of liked the Cheng paper since its so simple and I already have all the chemicals.

[Edit: Fixed some grammar mistakes]

[Edited on 20-5-2021 by Triflic Acid]




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[*] posted on 20-5-2021 at 10:05


Problem is EG is much less volatile than ethanol. So there's nothing driving the equilibrium towards your products other than initial concentrations.



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[*] posted on 20-5-2021 at 10:18


Shoot, maybe an alkoxide salt? That isn't volatile at all.



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[*] posted on 21-5-2021 at 10:16


Wait, I'm an idiot, the ethoxide will react with the ethylene glycol. Ethylene glycol has a pKa1 of ~15, around that of water.



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[*] posted on 21-5-2021 at 15:14


There's no clear "driving force".
But it's easy to add 20 times as much ethanol.
Then neutralise the catalyst and distill off a lot of "spare ethanol for re-use, some tetraethoxysilane as product , and finally some glycol.

Then play the game again with fresh catalyst and ethanol.
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[*] posted on 22-5-2021 at 07:51


And another note all together, would reacting sodium silicate with ethyl bromide make tetra ethyl orthosilicate? The constant ethanol cycle seems tiresome. Problem is that sodium silicate decomposes in most organic solvents . Would something like dioxane or dcm work?



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[*] posted on 22-5-2021 at 08:11


Supposing that the tetrakis-(2-hydroxyethoxy)-silane can be isolated and solubilized, one might consider the simple Williamson etherification to tetrakis-(2-methoxyethoxy)-silane with MeI and catalytic base. This should proceed easily at reasonable temperature, and while it won't make TEOS, it should be an effective replacement in any reaction calling for an orthosilicate.

Another, sort of weird possibility, is to try the rxn of your spiro-bis-ethylene-1,2-dioxysilane with diethoxymethane (bp 88 C) and some appropriate catalyst, with dioxolane (bp 74 C) forming and hopefully boiling off before any other component. If the reactions can proceed without reverting to silica, this system makes ethylene glycol (just barely) more volatile than ethanol! An excess of diethoxymethane may assist the equilibrium.




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 24-5-2021 at 03:30


https://en.wikipedia.org/wiki/Silicon_disulfide



If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

I can offer GC analysis of samples. Just U2U to me for more info.

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[*] posted on 24-5-2021 at 05:23


Thanks for that link Bedlasky. Ill run a few experiments to try and make that in good yield from silica gel and sulfur. If that doesn't work, I'll have to get out my precious silicon lumps and pulverize them.



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[*] posted on 24-5-2021 at 06:08


^The Wiki seems to say you need to use aluminium sulfide, not sulfur, to obtain this compound. I'd be amazed if sulfur would reduce silica.



[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 24-5-2021 at 07:14


Quote:

The material is formed by heating silicon and sulfur or by the exchange reaction between SiO2 and Al2S3


I think that heating sulfur might displace the oxygen, creating silicon disulfide. The oxygen would then react to make the SO2.




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[*] posted on 24-5-2021 at 07:18


I think you would need very high temperatures for that, maybe higher than the boiling point of sulfur.



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[*] posted on 24-5-2021 at 08:26


Boiling sulfur. What fun. I guess I'll stick to grinding up silicon and reacting that. Anyone have any experience with that reaction? Could I do it in a test tube or would a clay pot be needed?



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[*] posted on 25-5-2021 at 05:49


Quote: Originally posted by Triflic Acid  
Quote:

The material is formed by heating silicon and sulfur or by the exchange reaction between SiO2 and Al2S3


I think that heating sulfur might displace the oxygen, creating silicon disulfide. The oxygen would then react to make the SO2.


Silicon have very high affinity for oxygen. This reaction is very improbable.




If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

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[*] posted on 25-5-2021 at 08:38


Quote: Originally posted by Triflic Acid  
Boiling sulfur. What fun. I guess I'll stick to grinding up silicon and reacting that. Anyone have any experience with that reaction? Could I do it in a test tube or would a clay pot be needed?
Check out the autoignition temperature of sulfur. It's not a simple apparatus.



[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 25-5-2021 at 14:05


No, I meant if I'm using the silicon and sulfur method, not the silicon dioxide. That wouldn't need boiling sulfur, right?



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[*] posted on 3-6-2021 at 07:27


https://chemiday.com/reaction/3-1-0-11827Silicon (IV) fluoride react with ethanol



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