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Tetramethyl orthosilicate

Tetramethyl orthosilicate
IUPAC name tetramethoxysilane
Other names tetramethyl orthosilicate; methyl silicate; silicic acid, tetramethyl ester; silicon methoxide; TMOS
CAS number 681-84-5
PubChem 12682
Molecular formula SiC4H12O4
Molar mass 152.25
Appearance colourless liquid
Density 1.032
Melting point

4-5 °C

Boiling point

121–122 °C

Solubility in water organic solvents
Main hazards toxic
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Tetramethyl orthosilicate is the chemical compound with the formula Si(OCH3)4. This molecule consists of four methyl groups attached to the hypothetical anion SiO44-. The basic properties are similar to the more popular tetraethyl orthosilicate, which is usually preferred because the product of hydrolysis, ethanol, is less toxic than methanol.

Tetramethyl orthosilicate hydrolyzes to SiO2:

Si(OCH3)4 + 2 H2O → SiO2 + 4 CH3OH

In organic synthesis, Si(OCH3)4 has been used to convert ketones and aldehydes to the corresponding ketals and acetals, respectively.[1]


The hydrolysis of Si(OCH3)4 produces insoluble SiO2. Should this process occur in the eyes, vision would be impared.


  1. ^ Sakurai, H. "Silicon(IV) Methoxide" in Encyclopedia of Reagents for Organic Synthesis 2001 John Wiley & Sons. DOI: 10.1002/047084289X.rs012
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Tetramethyl_orthosilicate". A list of authors is available in Wikipedia.
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