Methyltrimethoxysilane is an
organosilicon compound
Organosilicon compounds are organometallic compounds containing carbon–silicon chemical bond, bonds. Organosilicon chemistry is the corresponding science of their preparation and properties. Most organosilicon compounds are similar to the ordin ...
with the formula CH
3Si(OCH
3)
3. It is a colorless, free-flowing liquid. It is a crosslinker in the preparation of
polysiloxane
A silicone or polysiloxane is a polymer made up of siloxane (−R2Si−O−SiR2−, where R = organic group). They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cooking ...
polymers.
Preparation, structure and reactivity
Methyltrimethoxysilane is usually prepared from
methyltrichlorosilane
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 reacti ...
and
methanol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...
:
:CH
3SiCl
3 + 3 CH
3OH → CH
3Si(OCH
3)
3 + 3 HCl
Alcoholysis of alkylchlorosilanes typically proceeds via an S
N2 mechanism. Inversion of the configuration is favored during nucleophilic attack when displacing good leaving groups, such as chloride. In contrast, displacement of poor leaving groups, such as
alkoxide
In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organic substituent. Alkoxides are strong bases and, whe ...
, retention is favored.
[Colvin, W. Ernest, ''Silicon in Organic Synthesis'', Butterworth and Co Ltd, 1981.]
Methyltrimethoxysilane is tetrahedral and is often described as sp
3 hybridized. It has idealized C
3v point symmetry
In geometry, a point reflection (point inversion, central inversion, or inversion through a point) is a type of isometry of Euclidean space. An object that is invariant under a point reflection is said to possess point symmetry; if it is invari ...
.
Hydrolysis of MTM proceeds both under acidic and basic conditions. Under acid conditions, rates of successive hydrolyses for methyltrimethoxysilane decreases with each step. Under basic condition the opposite is true.
[
]
See also
* Octadecyltrimethoxysilane
References
Silyl ethers
Alkoxides