Tetramethyl orthosilicate

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Tetramethyl orthosilicate
Tetramethyl orthosilicate.svg
Tetramethyl orthosilicate 3D.png
Names
IUPAC name
Tetramethyl orthosilicate
Other names
tetramethyl orthosilicate; methyl silicate; silicic acid, tetramethyl ester; silicon methoxide; TMOS
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.010.598 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/C4H12O4Si/c1-5-9(6-2,7-3)8-4/h1-4H3 Yes check.svgY
    Key: LFQCEHFDDXELDD-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C4H12O4Si/c1-5-9(6-2,7-3)8-4/h1-4H3
    Key: LFQCEHFDDXELDD-UHFFFAOYAT
  • CO[Si](OC)(OC)OC
Properties
SiC4H12O4
Molar mass 152.25
Appearancecolourless liquid
Density 1.032
Melting point 4 to 5 °C (39 to 41 °F; 277 to 278 K)
Boiling point 121 to 122 °C (250 to 252 °F; 394 to 395 K)
organic solvents
Vapor pressure 12 mmHg (25°C) [1]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
toxic
Flash point 96 °C; 205 °F; 369 K [1]
NIOSH (US health exposure limits):
PEL (Permissible)
none [1]
REL (Recommended)
TWA 1 ppm (6 mg/m3) [1]
IDLH (Immediate danger)
N.D. [1]
Related compounds
Other cations
Trimethyl borate
Trimethyl phosphite
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Tetramethyl orthosilicate (TMOS) is the chemical compound with the formula Si(OCH3)4. This molecule consists of four methoxy groups bonded to a silicon atom. The basic properties are similar to the more popular tetraethyl orthosilicate, which is usually preferred because the product of hydrolysis, ethanol, is less toxic than methanol.

Contents

Tetramethyl orthosilicate hydrolyzes to SiO2:

Si(OCH3)4 + 2 H2O → SiO2 + 4 CH3OH

In organic synthesis, Si(OCH3)4 has been used to convert ketones and aldehydes to the corresponding ketals and acetals, respectively. [2]

Safety

The hydrolysis of Si(OCH3)4 produces insoluble SiO2 and CH3OH (methanol). Even at low concentrations inhalation causes lung lesions, and at slightly higher concentrations eye contact with the vapor causes blindness[ citation needed ]. Worse, at low concentrations (200 ppm/15 min) the damage is often insidious, with onset of symptoms hours after exposure. [3] The mode of action is the precipitation of silica in the eyes and/or lungs[ citation needed ]. Contrary to common information, including several erroneous MSDS sheets, the methanol produced is only a risk through chronic exposure and is a comparatively small concern. The mechanisms of methanol toxicity are well established, methanol causes blindness via conversion to formaldehyde, then to toxic formic acid in the liver; methanol splashes to the eye cause only moderate and reversible eye irritation. [4]

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<span class="mw-page-title-main">2-Methoxyethanol</span> Chemical compound

2-Methoxyethanol, or methyl cellosolve, is an organic compound with formula C
3
H
8
O
2
that is used mainly as a solvent. It is a clear, colorless liquid with an ether-like odor. It is in a class of solvents known as glycol ethers which are notable for their ability to dissolve a variety of different types of chemical compounds and for their miscibility with water and other solvents. It can be formed by the nucleophilic attack of methanol on protonated ethylene oxide followed by proton transfer:

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3
F
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4
, or any of its salts and esters. It is one of the silicate anions. It is occasionally called the silicon tetroxide anion or group.

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References

  1. 1 2 3 4 5 NIOSH Pocket Guide to Chemical Hazards. "#0428". National Institute for Occupational Safety and Health (NIOSH).
  2. Sakurai, H. "Silicon(IV) Methoxide" in Encyclopedia of Reagents for Organic Synthesis 2001 John Wiley & Sons. doi : 10.1002/047084289X.rs012
  3. "Tetramethyl silicate". National Library of Medicine - Hazardous Substances Data Bank. National Library of Medicine. Retrieved 11 February 2013.
  4. "Methanol". Hazardous Substances Data Bank - National Library of Medicine. National Library of Medicine. Retrieved 11 February 2013.