Tetramethylsilane is a chemical compound whose molecular structure is a derivative of silane (SiH₄) with four methyl groups substituted for the four hydrogen atoms in it. The acronym TMS is very commonly used for this highly volatile organic compound which contains a silicon atom in the center. Tetramethylsilane has the chemical formula C₄H₁₂Si and the chemical structure shown in the infobox. A structural chemical formula could be written as Si(CH₃)₄ where -CH₃ is a methyl group.

Uses

Tetramethylsilane is used as an internal standard for calibrating chemical shift in ¹H and ¹³C NMR spectroscopy. Because all twelve hydrogen atoms in a tetramethylsilane molecule are equivalent, they show up as a singlet peak in an ¹H NMR spectrum. The chemical shift of this singlet is considered to be δ0.0 in the spectrum and all other chemical shifts are determined relative to it. The silicon in tetramethylsilane shifts its ¹H NMR signal upfield. The vast majority of compounds studied by ¹H NMR have hydrogen peaks downfield of the tetramethylsilane peak, so there is usually no interefence between this standard peak and the sample peaks, and the tetramethylsilane singlet can usually easily be identified for the chemical shift calibration.

Similarly, all four carbon atoms in a tetramethylsilane molecule are equivalent. In a fully decoupled ¹³C NMR spectrum, the carbon in the tetramethylsilane also shows up as a singlet, allowing for easier identification. The chemical shift of this singlet is also set to be δ0.0 in the ¹³C spectrum and all other chemical shifts are determined relative to it.

A supply of tetramethylsilane is usually kept as a refrigerated liquid because otherwise, it could easily evaporate away. The symmetry of the tetramethylsilane molecule makes it a non-polar compound.

Tetramethylsilane is used in chemical vapor deposition processes to create thin layers of silicon dioxide or silicon carbide.

External links

Silicon compounds | Organometallic compounds

Tetramethylsilan