This MedLibrary.org supplementary page on Tetraethyl orthosilicate is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
| Tetraethyl orthosilicate | |
|---|---|
 |
 |
| IUPAC name | tetraethoxysilane |
| Other names | tetraethyl orthosilicate; ethyl silicate; silicic acid, tetraethyl ester; silicon ethoxide; TEOS |
| Identifiers | |
| CAS number | 78-10-4 |
| PubChem | |
| Properties | |
| Molecular formula | SiC8H20O4 |
| Molar mass | 208.32 |
| Appearance | colourless liquid |
| Density | 0.94 |
| Melting point |
-77 °C |
| Boiling point |
166-169 °C |
| Solubility in water | decomp |
| Hazards | |
| Main hazards | Toxic |
| Flash point | 45 °C |
| 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 SiO44- ion, which is called orthosilicate. As an ion in solution, 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 HCl
where R = alkyl such as methyl, ethyl, propyl, etc.
Applications
TEOS is mainly used as a crosslinking agent in silicone polymers. Other applications include coatings for carpets and other objects. These applications exploit the reactivity of the Si-OR bonds.1
Other reactions
TEOS has the remarkable property of easily converting into silicon dioxide. This reaction occurs upon the addition of water:
- Si(OC2H5)4 + 2 H2O → SiO2 + 4 C2H5OH
This hydrolysis reaction is an example of a sol-gel process. The side product is ethanol. The reaction proceeds via a series of condensation reactions that convert the TEOS molecule into a mineral-like solid via the formation of Si-O-Si linkages. Rates of this conversion are sensitive to the presence of acids and bases, both of which serve as catalysts.
At elevated temperatures (>600 °C), TEOS converts to silicon dioxide:
- Si(OC2H5)4 → SiO2 + 2O(C2H5)2
The volatile coproduct is diethylether.
References
- ^ Lutz Rösch, Peter John, Rudolf Reitmeier "Silicon Compounds, Organic" Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a24_021. Article Online Posting Date: June 15, 2000
Wikipedia content modification information:
- This page was last modified on 1 December 2008, at 20:46.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Tetraethyl orthosilicate".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.