Tetramethoxysilane , 98% , 681-84-5
Synonym(s):
Tetramethoxysilane;Tetramethyl orthosilicate
CAS NO.：681-84-5
Empirical Formula: C4H12O4Si
Molecular Weight: 152.22
MDL number: MFCD00008341
EINECS: 211-656-4
PRODUCT Properties
| Melting point: | −4 °C(lit.) |
| Boiling point: | 121-122 °C(lit.) |
| Density | 1.023 g/mL at 25 °C(lit.) |
| vapor density | 5.25 (vs air) |
| vapor pressure | 3.35 psi ( 20 °C) |
| FEMA | 3185 | METHYLATED SILICA |
| refractive index | n |
| Flash point: | 84 °F |
| storage temp. | Store below +30°C. |
| form | liquid |
| Specific Gravity | 1.032 |
| color | colorless |
| explosive limit | 0.88-23.8%(V) |
| Water Solubility | hydrolysis |
| Sensitive | Moisture Sensitive |
| Hydrolytic Sensitivity | 7: reacts slowly with moisture/water |
| BRN | 1699658 |
| InChIKey | LFQCEHFDDXELDD-UHFFFAOYSA-N |
Description and Uses
Tetramethyl orthosilicate is the chemical compound with the formula Si(OCH3)4. This molecule consists of four methoxy groups bonded to a silicon atom.
Two common organic precursors are tetraethyl orthosilicate (TEOS) and tetramethyl orthosilicate (TMOS). The latter is more toxic than the former.
Tetraethyl orthosilicate (TEOS), Si(OC2H5)4, is the first alkoxide of the series, followed by tetramethyl orthosilicate (TMOS), Si(OCH3)4, which is, however, less safe to handle and hydrolyzes faster than TEOS.
The hydrolysis of TMOS is, in fact, around six times faster: in general, a lower hydrolysis rate is associated with an increase of the organic group size in the silicon alkoxide. The properties of the silicon alkoxides change according to the dimension of the alkoxy; larger groups produce an increase in molecular weight, viscosity, and boiling point and a decrease in density of the alkoxides.
As a rule of thumb, a larger size of the alkoxy group is associated with a lower hydrolysis rate due to the steric hindrance. The reactivity follows the sequence, with tetramethyl orthosilicate the most reactive alkoxide:
tetramethyl orthosilicate >tetraethyl orthosilicate>tetra-n-propylorthosilicate>tetrabutyl orthosilicate
Tetramethyl orthosilicate (TMOS) is popularly used in the sol-gel synthesis of silicates1 and chromium-doped silicates and in the formation of hexagonal mesoporous silica layers.
Safety
| Symbol(GHS) |    GHS02,GHS05,GHS06 |
| Signal word | Danger |
| Hazard statements | H226-H315-H318-H330 |
| Precautionary statements | P210-P233-P280-P303+P361+P353-P304+P340+P310-P305+P351+P338 |
| Hazard Codes | T+ |
| Risk Statements | 10-26-37/38-41 |
| Safety Statements | 16-26-36/37/39-45-28A |
| RIDADR | UN 2606 6.1/PG 1 |
| OEB | B |
| OEL | TWA: 1 ppm (6 mg/m3) |
| WGK Germany | 3 |
| RTECS | VV9800000 |
| F | 10-21 |
| Autoignition Temperature | 245 °C |
| TSCA | Yes |
| HazardClass | 6.1 |
| PackingGroup | I |
| HS Code | 29209085 |
