nuclear
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tetraethyl silicate production?
Does anybody have a synthesis for tetraethyl silicate (ortosilicate)?
Maybe with esterification: H4SiO4/ ethanol/ H2SO4 and destilation?
But i`m not sure if this true and possible. 
[Edited on 12-6-2006 by nuclear]
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kazaa81
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Maybe you mean tetraethyl silane?
However, the silicic acid doesn't seem to me very stable...maybe H2SiO3 is more stable.
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unionised
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My guess is that he means what he says.
IIRC SiCl4+ 4ETOH --> Si(OET)4 + 4HCl.
I'm not so sure how to get SiCl4 except from Cl2 and Si and I'm not sure that's easy.
On the other hand, some silicone sealants contain Si(OET)4- you might be able to distil it.
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BromicAcid
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If you tried your esterfication it would fail, at least from what I know. Adding acid to solutions of silic acid results in the precipitation of
SiO<sub>2</sub> from the solution somewhat rapidly. Unfortunately I don't know a synthesis off hand.
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chemoleo
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Well, tetramethyl silicate is highly susceptible to hydrolysis, it is used to make voluminous silica gels. Thus it follows that esterification of
silicic acid with MeOH in aqueous medium won't work.
The tetraethyl silicate doesn't hydrolyse quickly, however. It is more stable with water. I'd doubt again though that it can be made by direct
esterification.
SiCl4 + 4 EtOH seems like the best guess - the problem being the making of SiCl4 of course.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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nuclear
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| Quote: | Originally posted by unionised
On the other hand, some silicone sealants contain Si(OET)4- you might be able to distil it. |
Some catalysts for silicone (C-5) contains Si(OET)4. But these catalysts (25g) contains about 45-47% Si(OET)4, 32-34% dibutyltin dilaurate.. and it`s
expensive.
I need Si(OET)4 for pure silica, (aerogels), solid phase for organic synthesis.. many things.
Silica from Na2SiO3 and HCl probably contain impurities as NaCl or something else. It`s only for absorption moisture.
[Edited on 13-6-2006 by nuclear]
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kazaa81
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Brauer shows SiCl4 preparation as an addition of Cl2 to powdered Si, this last heated by a furnace.
Seems not so easy. It's properties remind me SnCl4 (colorless liquid that fumes heavily if exposed to air).
It is also wrote that SiCl4 forms esters of silicic acid upon addition to alcohols.
[Edited on 13-6-2006 by kazaa81]
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turd
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While your DIY-spirit is laudable, please consider that TEOS is a totally unsuspicious industry chemical. Just have someone order it for you.
That being said, TEOS gels are really cool for growing crystals by slow diffusion.
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unionised
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"please consider that TEOS is a totally unsuspicious industry chemical."
Add water; filter; drink.
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chemoleo
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Err.. turd, what are you referrring to?
TEOS?
Growing crystals in them...do you have more information of this? Would it work, i.e. with glycerol, or PEG, for inorganic salts? I suppose it does
work with protein crystallography...where polymers are used all the time.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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chemoleo
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Did you delete these posts, Turd, Neutrino?? What happened to them? Am I going 'slightly mad'? Two at the same time, from different authors?
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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unionised
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"Err.. turd, what are you referrring to?
TEOS?"
Tetra Ethyl Ortho Silicate; the stuff in the thread's title.
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neutrino
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The forum went down for a few hours yesterday. I guess the posts went with it.
To recap:
TEOS = Tetra Ethyl Ortho Silicate
TMOS = Tetra Methyl Ortho Silicate
Both are used in aerogel production, but TEOS is preferred due to its lower toxicity. TEOS is relatively cheap: Acros charges US$15 for 250mL, 95%
pure.
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turd
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Must have been a database glitch... :/
To make a long story short: Testtube having silica gel with one reagent on bottom and aqueous solution with other reagent on top can give, after a few
months, crystals suitable for X-ray diffraction. Low concentrations are mandatory.
Some examples of this method are found in the literature.
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12AX7
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| Quote: | Originally posted by chemoleo
Did you delete these posts, Turd, Neutrino?? What happened to them? Am I going 'slightly mad'? Two at the same time, from different authors?
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I've noticed posts disappearing too, I swear I posted a thorough message in that Tunguska thread.
Tim
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