Methyltrichlorosilane: Difference between revisions

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| Verifiedfields = changed

| verifiedrevid = 412829925

| PIN = Trichloro(methyl)silane

|Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = UIR5I18638

| EINECS = 200-902-6

| PubChem = 6399

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChemSpiderID = 6159

| SMILES = C[Si](Cl)(Cl)Cl

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 1S/CH3Cl3Si/c1-5(2,3)4/h1H3

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = JLUFWMXJHAVVNN-UHFFFAOYSA-N }}

|Section2={{Chembox Properties

| Appearance = Colorless liquid

| Density = 1.273{{nbsp}}g·cm⁻³

| MeltingPtC = -77

| BoilingPtC = 66

| Solubility = Reacts with water

| SolubleOther =

| MagSus = −87.45·10⁻⁶{{nbsp}}cm³·mol{{sup|−1}}}}

|Section3={{Chembox Hazards

| GHSPictograms = {{GHS02}}{{GHS07}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|225|315|319|335}}

| PPhrases = {{P-phrases|210|233|240|241|242|243|261|264|271|280|302+352|303+361+353|304+340|305+351+338|312|321|332+313|337+313|362|370+378|403+233|403+235|405|501}}

| NFPA-H = 3

| NFPA-F = 3

| NFPA-R = 2

| NFPA-S = W

| ExternalSDS = [http://fscimage.fishersci.com/msds/86261.htm Fischer Scientific MSDS]

| MainHazards = Highly flammable, reacts with water to release [[Hydrogen chloride|HCl]]

| FlashPtC = 8.0

| AutoignitionPtC = 490

}}

'''Methyltrichlorosilane''', also known as '''trichloromethylsilane''', is a [[monomer]] and [[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.

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{{nbsp}}°C.<ref name = silicon>Rösch, L; et al. "Silicon Compounds, Organic." Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim, 2005. {{doi|10.1002/14356007.a24_021}}</ref>

: 2 CH₃Cl + Si → (CH₃)_4−nSiCl_n + 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.<ref>Rochow, E. The Direct Synthesis of Organosilicon Compounds. ''J. Am. Chem. Soc.'' '''1945''', ''67'', 963. {{doi|10.1021/ja01222a026}}</ref> Even though [[dimethyldichlorosilane]] is usually the major product, if methyltrichlorosilane is needed, the amount of metal catalyst is reduced.<ref name = silicon/>

==Reactions==

===Hydrolysis and alcoholysis===

Methyltrichlorosilane undergoes hydrolysis, shown in idealized form here:<ref name = silicon/>

: MeSiCl₃ + 3 H₂O → MeSi(OH)₃ + 3 HCl

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

: MeSi(OH)₃ → MeSiO_1.5 + 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 + 3''n'' Na →[MeSi]_''n'' + 3''n'' 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]].<ref>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.</ref>

==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{{nbsp}}°C in a vacuum, making it an ideal material for electrical insulation at high temperatures.<ref name = silicon/> 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.<ref name = chemistry>Rochow, E. "An Introduction to the Chemistry of the Silicones." New York: John Wiley & Sons, Inc., 1946. {{ISBN|1-4437-2286-3}}</ref> 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.<ref name = chemistry/>

===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

[[Ester]]s and [[lactone]]s can also be cleaved with methyltrichlorosilane and sodium iodide to give the corresponding [[carboxylic acid]]s. [[Acetal]]s convert to carbonyl compounds. Thus, methyltrichlorosilane can be used to remove acetal [[protecting group]]s from carbonyl compounds under mild conditions.<ref name = eros>Olah, G; et al. "Methyltrichlorosilane." Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons, Inc., 2001. {{doi|10.1002/047084289X.rm265}}</ref>

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

Methyltrichlorosilane and sodium iodide can be used as a means of converting [[Alcohol (chemistry)|alcohol]]s to their corresponding [[Organoiodine compound|iodides]]; however, this reaction does not work as well with primary alcohols.<ref name = eros/>

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

===Silicon carbide epitaxy===

Methyltrichlorosilane is used as a reagent in [[silicon carbide]] [[epitaxy]] to introduce chloride in the gas phase. Chloride is used to reduce the tendency of silicon to react in the gas phase and thus to increase the growth rate of the process.<ref name = MTS>Bosi, M; et al. "Defect structure and strain reduction of 3C-SiC/Si layers obtained with the use of a buffer layer and methyltrichlorosilane addition" CrystEngComm 2016, 18, 2770-2779 {{doi| 10.1039/C6CE00280C}}</ref> Methyltrichlorosilane is an alternative to [[HCl]] gas or to [[trichlorosilane]].

{{commons category|Methyltrichlorosilane|lcfirst=yes}}