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Tetraethyl orthosilicate
Tetraethyl orthosilicate is the major 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. Additional recommended knowledgeTEOS is a tetrahedral molecule. Many analogues exist, and most are prepared by alcoholysis of silicon tetrachloride:
where R = alkyl such as methyl, ethyl, propyl, etc. ApplicationsTEOS has many remarkable properties, but perhaps the most useful is its easy conversion into silicon dioxide. This reaction occurs upon the addition of water:
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:
The volatile coproduct is diethylether. |
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Tetraethyl_orthosilicate". A list of authors is available in Wikipedia. |