Wikipedia
Tetraethyl orthosilicate
Tetraethyl orthosilicate is the chemical compound with the formula Si(OCH). Often abbreviated TEOS, it is a colorless liquid that degrades in water. TEOS is the ethyl ether of orthosilicic acid, Si(OH). It is a prototypical alkoxide.
TEOS is a tetrahedral molecule. Like its many analogues, TEOS is prepared by alcoholysis of silicon tetrachloride:
SiCl + 4 EtOH → Si(OEt) + 4 HClwhere Et = CH.