Ethyl Silicate

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, 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.