RAMAN STUDIES OF THE HYDROLYSIS OF TETRAMETHYL ORTHOSILICATE .1. INFLUENCE OF FORMAMIDE ON THE PH

Raman spectra of tetramethyl orthosilicate (TMOS) solutions undergoing hydrolysis are presented. Signals near 830 cm-1, previously assigned to a Si-O vibration, faded as the water:TMOS mole ratio increased from 2:1 to 10:1. A signal at 795 cm-1 was observed at low pH values, which we assigned to Si(OH)4. Next, the simultaneous evolution of the pH and the Raman spectra of TMOS solutions, with and without formamide, were examined. The solutions with formamide showed a pH change, consistently reaching a final pH near 4.7 when the initial pH was between 2 and 5.5. The pH variation, caused by the hydrolysis of formamide, is the primary factor involved in influencing the TMOS hydrolysis. © 1990 American Chemical Society.