Tetraethyl orthosilicate 1

Tetraethyl orthosilicate

Tetraethyl orthosilicate

Identifiers

CAS number 78-10-4 [1] 

PubChem 6517 [2]

ChemSpider 6270 [3] 

Jmol-3D images Image 1 [4]

Properties

Molecular formula SiC8H20O4

Molar mass 208.33 g mol−1

Appearance colourless liquid

Density 0.933 g/mL at 20°C

Melting point −77 °C, 196 K, -107 °F

Boiling point 166-169 °C, 439-442 K, 331-336 °F

Solubility in water miscible, but readily decomposes

Hazards

Main hazards Flammable, Harmful by inhalation

Flash point 45 °C

  (verify) [5] (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

Infobox references

Tetraethyl orthosilicate is the chemical compound with the formula Si(OC2H5)4. Often abbreviated TEOS, this molecule consists of four ethyl groups attached to SiO4

4− ion, which is called orthosilicate. As an ion in solution,

Tetraethyl orthosilicate 2

orthosilicate does not exist. Alternatively TEOS can be considered to be the ethyl ester of orthosilicic acid, Si(OH)4.It is a prototypical alkoxide.TEOS is a tetrahedral molecule. Many analogues exist, and most are prepared by alcoholysis of silicon tetrachloride:

SiCl4 + 4 ROH → Si(OR)4 + 4 HClwhere R = alkyl such as methyl, ethyl, propyl, etc.

ApplicationsTEOS is mainly used as a crosslinking agent in silicone polymers and as a precursor to silicon dioxide in thesemiconductor industry.[6] Other applications include coatings for carpets and other objects. TEOS is used in theproduction of aerogel. These applications exploit the reactivity of the Si-OR bonds.[7]

Other reactionsTEOS has the remarkable property of easily converting into silicon dioxide. This reaction occurs upon the additionof water:

Si(OC2H5)4 + 2 H2O → SiO2 + 4 C2H5OHThis hydrolysis reaction is an example of a sol-gel process. The side product is ethanol. The reaction proceeds via aseries of condensation reactions that convert the TEOS molecule into a mineral-like solid via the formation ofSi-O-Si linkages. Rates of this conversion are sensitive to the presence of acids and bases, both of which serve ascatalysts. The Stöber process allows the formation of monodisperse silica particles.At elevated temperatures (>600 °C), TEOS converts to silicon dioxide:

Si(OC2H5)4 → SiO2 + 2 (C2H5)2OThe volatile coproduct is diethyl ether.

References[1] http:/ / www. commonchemistry. org/ ChemicalDetail. aspx?ref=78-10-4[2] http:/ / pubchem. ncbi. nlm. nih. gov/ summary/ summary. cgi?cid=6517[3] http:/ / www. chemspider. com/ 6270[4] http:/ / chemapps. stolaf. edu/ jmol/ jmol. php?model=CCO%5BSi%5D%28OCC%29%28OCC%29OCC[5] http:/ / en. wikipedia. org/ w/ index. php?title=Special:ComparePages& rev1=470603747& page2=Tetraethyl+ orthosilicate[6] D. Bulla, Deposition of thick TEOS PECVD silicon oxide layers for integrated optical waveguide applications. Thin Solid Films. 1998;

334(1-2):60-64. Available at: http:/ / linkinghub. elsevier. com/ retrieve/ pii/ S0040609098011171.[7][7] Lutz Rösch, Peter John, Rudolf Reitmeier "Silicon Compounds, Organic" Ullmann's Encyclopedia of Industrial Chemistry, 2002,

Wiley-VCH, Weinheim. . Article Online Posting Date: June 15, 2000

External links• NIST Standard Reference Database 69, June 2005 Release: NIST Chemistry WebBook (http:/ / webbook. nist.

gov/ cgi/ cbook. cgi?ID=C78104)• Details of TEOS deposition process (http:/ / timedomaincvd. com/ CVD_Fundamentals/ films/

TEOS_O2_thermal. html)• CDC - NIOSH Pocket Guide to Chemical Hazards (http:/ / www. cdc. gov/ niosh/ npg/ npgd0282. html)

Article Sources and Contributors 3

Article Sources and ContributorsTetraethyl orthosilicate  Source: http://en.wikipedia.org/w/index.php?oldid=577710285  Contributors: 2001:620:40B:1090:1C00:B4E5:754C:3339, A876, Akiry, Ambix, Andi47, Beetstra,Carlog3, Chem-awb, Chris the speller, DutchDevil, Fvasconcellos, Graeme Bartlett, JWBE, JZNIOSH, Jkr2255, Kaos-pheory, Keenan Pepper, Kupirijo, Lamro, Mshearn, Penguinoid, PlasmicPhysics, Rembecki, Smokefoot, Suchirera, TMaster, Tomaxer, V8rik, Whoop whoop pull up, 17 anonymous edits

Image Sources, Licenses and ContributorsImage:Tetraethyl orthosilicate.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Tetraethyl_orthosilicate.svg  License: Public Domain  Contributors: Fvasconcellos 16:01, 7 May 2007(UTC)Image:Tetraethyl orthosilicate 3D.png  Source: http://en.wikipedia.org/w/index.php?title=File:Tetraethyl_orthosilicate_3D.png  License: Public Domain  Contributors: Fvasconcellos 16:03, 7May 2007 (UTC)File:Yes check.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Yes_check.svg  License: Public Domain  Contributors: AnomieFile:X mark.svg  Source: http://en.wikipedia.org/w/index.php?title=File:X_mark.svg  License: Public Domain  Contributors: User:Gmaxwell

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