Methyltrichlorosilane

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Methyltrichlorosilane
Names
IUPAC name
Trichloromethylsilane
Other names
Methyltrichlorosilane
Identifiers
75-79-6 YesY
ChemSpider 6159 N
EC Number 200-902-6
Jmol interactive 3D Image
PubChem 6399
Properties
CH3Cl3Si
Molar mass 149.47 g·mol−1
Appearance colorless liquid
Density 1.273 g cm−3
Melting point −77 °C (−107 °F; 196 K)
Boiling point 66 °C (151 °F; 339 K)
reaction in water
Solubility soluble in methylene chloride
Hazards
Main hazards Highly flammable, reacts violently with water
Safety data sheet Fischer Scientific MSDS
F Xi
R-phrases R11, R14, R36/37/38
S-phrases (S2), S26, S39
NFPA 704
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g., gasoline) Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond
3
3
2
Flash point 8.0 °C (46.4 °F; 281.1 K)
490 °C (914 °F; 763 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Methyltrichlorosilane, also known as trichloromethylsilane, is an organosilicon compound with the formula CH3SiCl3. It is a colorless liquid with a sharp odor similar to that of hydrochloric acid. As methyltrichlorosilane is a reactive compound, it is mainly used a precursor for forming various cross-linked siloxane polymers.

Preparation

Methyltrichlorosilane results from the direct process of chloromethane with elemental silicon in the presence of a copper catalyst, usually at a temperature of at least 250 °C.[1]

2 CH3Cl + Si → (CH3)4-nSiCln + other products

While this reaction is the standard in industrial silicone production and is nearly identical to the first direct synthesis of methyltrichlorosilane, the overall process is inefficient with respect to methyltrichlorosilane.[2] Even though dimethyldichlorosilane is usually the major product, if methyltrichlorosilane is needed, the amount of metal catalyst is reduced.[1]

Reactions

Hydrolysis and alcoholysis

Methyltrichlorosilane undergoes hydrolysis, shown in idealized form here:[1]

MeSiCl3 + 3 H2O → MeSi(OH)3 + 3 HCl

The silanol is unstable and will eventually condense to give a polymer network:

MeSi(OH)3 → MeSiO1.5 + 1.5 H2O

Methyltrichlorosilane undergoes alcoholysis (reaction with alcohol) to give alkoxysilanes. Methanol converts it to trimethoxymethylsilane:

MeSiCl3 + 3 CH3OH → MeSi(OCH3)3 + 3 HCl

Reduction

Reduction of methyltrichlorosilane with alkali metals forms a highly crosslinked material called poly(methylsilyne):

n MeSiCl3 + 3n Na →[MeSi]n + 3n NaCl

The reaction illustrates the susceptibility of silicon halides to reductive coupling. Poly(methylsilyne) is soluble in organic solvents, and can be applied to surfaces before being pyrolyzed to give the ceramic material, silicon carbide.[3]

Applications

Conversion to polymers and resins

One use for methyltrichlorosilane is in the production of methyl silicone resins (highly crosslinked polymers). Because of the stability of the cross-linked polymers resulting from condensation, the resin is stable to 550 °C in a vacuum, making it an ideal material for electrical insulation at high temperatures.[1] These resins can be used to coat computer chips or other electronic parts since they both repel water and provide thermal isolation. .

Surface treatments

Methyltrichlorosilane vapor reacts with water on surfaces to give a thin layer of methylpolysiloxane, which changes the contact angle of the surface to water. This effect arises because of the oriented layer of methyl groups, making a water-repellent film.[4] Filter paper treated with methyltrichlorosilane allows organic solvents to pass through, but not water. Another benefit of such water-repellent films is that the polymers formed are stable: one of the only ways to remove the siloxane film is by acid strong enough to dissolve silicone.[4]

Reagent in organic synthesis

A combination of methyltrichlorosilane and sodium iodide can be used to cleave carbon-oxygen bonds such as methyl ethers.

R'OR + MeSiCl3 + NaI + H2O → R'OH + RI + MeSiCl2(OH) + NaCl

Esters and lactones can also be cleaved with methyltrichlorosilane and sodium iodide to give the corresponding carboxylic acids. Acetals convert to carbonyl compounds. Thus, methyltrichlorosilane can be used to remove acetal protecting groups from carbonyl compounds under mild conditions.[5]

RR'C(OMe)2 + MeSiCl3 + NaI → RR'CO + 2 MeI + MeSiCl2(OMe) + NaCl

Finally, methyltrichlorosilane and sodium iodide can be used as a means of converting alcohols to their corresponding iodides; however, this reaction does not work as well with primary alcohols.[5]

ROH + MeSiCl3 + NaI → RI + MeSiCl2(OH) + NaCl

References

  1. 1 2 3 4 Rösch, L; et al. "Silicon Compounds, Organic." Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a24_021
  2. ↑ Rochow, E. The Direct Synthesis of Organosilicon Compounds. J. Am. Chem. Soc. 1945, 67, 963. doi:10.1021/ja01222a026
  3. ↑ Bianconi, Patricia A.; Pitcher, Michael W.; Joray, Scott. "A method of preparing poly(methyl- or ethyl-silyne) and silicon carbide ceramics therefrom." U.S. (2006), 15 pp. CODEN: USXXAM US 6989428 B1 20060124 CAN 144:129423 AN 2006:65860.
  4. 1 2 Rochow, E. "An Introduction to the Chemistry of the Silicones." New York: John Wiley & Sons, Inc., 1946. ISBN 1-4437-2286-3
  5. 1 2 Olah, G; et al. "Methyltrichlorosilane." Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons, Inc., 2001. doi:10.1002/047084289X.rm265
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