What Is Tetramethylsilane?
Tetramethylsilane (TMS), an organosilicon compound, has the molecular formula Si(CH3)4 or SiMe4. With a CAS number of 75-76-3, TMS is a clear colorless liquid at room temperature, characterized by its petroleum odor. It has a molecular weight of 88.23, a melting point of -152°F, a boiling point of 79.9°F, and a density of 0.648 g/cm3. TMS is extremely soluble in ethanol and diethyl ether, but almost insoluble in water. It is highly flammable and should be handled with care, being stable under normal conditions but reactive with strong oxidizers, acids, and bases.
Uses of Tetramethylsilane
Tetramethylsilane is mainly used as an internal standard in NMR spectroscopy and as a precursor for silicon dioxide and silicon carbide in chemical vapor deposition (CVD). In NMR, TMS’s NMR peak shifts significantly towards the low-frequency side, making it ideal for use as a reference material. It is chemically unreactive, highly volatile, and easily removable post-NMR measurement. In CVD, TMS serves as a precursor to silicon dioxide or silicon carbide, depending on the growth conditions.
Principle of Tetramethylsilane
1. Synthesis:
In the lab, TMS is synthesized by reacting chlorotrimethylsilane or silicon tetrachloride with methylmagnesium bromide in dry dibutyl ether, followed by purification.
2. Chemical Reaction:
TMS can react with n-butyl lithium to form Si(CH3)3CH2Li, used as an alkylation reagent. It is also a byproduct in the formation of methylchlorosilane from the reaction of chloromethane and silicon.
Types of Tetramethylsilane
Sold primarily as a chemical reagent, TMS is available in various volumes for use in biochemistry, NMR measurements, and as an internal standard reagent. Due to its low boiling point, it requires refrigeration for storage.