Tetraethyl orthosilicate

Tetraethyl orthosilicate is the chemical compound with the formula Si(OC₂H₅)₄. Often abbreviated TEOS, it is a colorless liquid that degrades in water. TEOS is the ethyl ester of orthosilicic acid, Si(OH)₄. It is a prototypical alkoxide.

TEOS is a tetrahedral molecule. Like its many analogues, TEOS is prepared by alcoholysis of silicon tetrachloride: