Tetramethylorthosilicate

Structural formula
General
Surname	Tetramethylorthosilicate
other names	Tetramethyl orthosilicate; Tetramethyl silicate; Methyl silicate; TMOS;
Molecular formula	C 4 H 12 O 4 Si
Brief description	colorless liquid with an ethereal odor
External identifiers / databases
EC number	211-656-4
ECHA InfoCard	100.010.598
PubChem	12682
ChemSpider	12161
Wikidata	Q377159
properties
Molar mass	152.22 g mol −1
Physical state	liquid
density	1.03 g cm −3
Melting point	−2 ° C
boiling point	122 ° C
Vapor pressure	13 h Pa (20 ° C); 18 hPa (25 ° C);
solubility	Decomposes in water
Refractive index	1.3683 (20 ° C)
safety instructions
H and P phrases	H: 226-315-318-330
	P: 210-260-280-304 + 340 + 310-305 + 351 + 338 + 310-370 + 378
MAK	Switzerland: 1 ml m −3 or 6 mg m −3
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Tetramethylorthosilicate (also tetramethoxysilane , silicic acid tetramethyl ester or methyl silicate , TMOS for short ) is a colorless liquid.

Extraction and presentation

Tetramethylorthosilicate can be obtained by reacting silicon tetrachloride with methanol .

{\ displaystyle \ mathrm {SiCl_ {4} +4 \ CH_ {3} OH \ longrightarrow Si (OCH_ {3}) _ {4} +4 \ HCl}}

properties

Tetramethylorthosilicate slowly hydrolyzes with water to form orthosilicic acid and methanol :

{\ displaystyle \ mathrm {C_ {4} H_ {12} O_ {4} Si + 4 \ H_ {2} O \ longrightarrow H_ {4} SiO_ {4} +4 \ CH_ {3} OH}}

TMOS is flammable and toxic.

Tetramethylorthosilicate forms highly flammable vapor-air mixtures. The compound has a flash point of 26 ° C. The explosion range is between 0.88% by volume as the lower explosion limit (LEL) and 23.8% by volume as the upper explosion limit (UEL). The ignition temperature is 245 ° C. The substance therefore falls into temperature class T3.

use

It is used in sol-gel processes as silica - precursor for the preparation of gels used especially silica aerogels . The compound is sparingly soluble in water; an alcohol is therefore usually used as the reaction medium as a solubilizer.

safety instructions

Contact of tetramethylorthosilicate with the skin causes redness and pain. Contact with the vapors can cause irritation and redness in the eyes. Inhalation causes a burning sensation, a sore throat and cough and can lead to pulmonary edema, kidneys and liver can also be damaged. If swallowed, stomach pain may occur. Risk of blindness through inhalation (releases methanol in the blood).

The vapors of tetramethylorthosilicate can form an explosive mixture with air ( flash point 26 ° C, ignition temperature 240 ° C).

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m Entry on tetramethyl orthosilicate in the GESTIS substance database of the IFA , accessed on August 21, 2019(JavaScript required) .
↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-480.
↑ Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for 681-84-5 or tetramethylorthosilicate ), accessed on November 2, 2015.
↑ Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , p. 702.

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m Entry on tetramethyl orthosilicate in the GESTIS substance database of the IFA , accessed on August 21, 2019(JavaScript required) .

[CRC90_3_480-2] David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-480.

[3] Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for 681-84-5 or tetramethylorthosilicate ), accessed on November 2, 2015.

[brauer-4] Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , p. 702.