Tetramethylsilane
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| Tetramethylsilane | |
|---|---|
| Image:Tetramethylsilane.PNG Image:Tetramethylsilane-2D-skeletal.png Image:Tetramethylsilane-3D-vdW.png | |
| General | |
| Systematic name | Tetramethylsilane |
| Other names | TMS |
| Molecular formula | C4H12Si |
| SMILES | C[Si](C)(C)C |
| Molar mass | 88.2248 g/mol |
| Appearance | Colourless liquid. |
| CAS number | [75-76-3] [1] |
| Properties | |
| Density and phase | 0.648 g/cm-3, liquid. |
| Solubility in water | low |
| Other solvents | most organic solvents |
| Melting point | -99.06 °C (174.09 K) |
| Boiling point | 26.6 °C (299.75 K) |
| Viscosity | ? cP at ?°C |
| Structure | |
| Molecular shape | Tetrahedral |
| Dipole moment | 0 D |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | Flammable. |
| NFPA 704 | |
| Flash point | -28 °C |
| R/S statement | R: R20, R36, R37, R38. S: S16, S24/25, S7/9. |
| RTECS number | VV5705400 |
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR δ0 |
| Related compounds | |
| Related compounds | silane neopentane isobutane hexamethyldisiloxane |
| Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references | |
Tetramethylsilane, or TMS, is a chemical compound with the formula Si(CH3)4 or SiMe4 (Me = CH3). Like the parent, it is tetrahedral with four methyl groups substituted for the four hydrogen atoms in it. Because of its high volatility, TMS is usually refrigerated. The symmetry of the tetramethylsilane molecule makes it a non-polar compound.
[edit] Synthesis and reactions
TMS is a by-product of the production of methyl chlorosilanes, SiClx(CH3)4-x, via the "direct reaction" of methyl chloride with silicon. The more useful products of this reaction are those for x = 1, 2, and 3.
TMS undergoes deprotonation by treatment with butyl lithium to give Si(CH3)3CH2Li. The latter, trimethylsilylmethyl lithium, is a relatively common alkylating agent.
Tetramethylsilane is used in chemical vapor deposition processes to create thin layers of silicon dioxide or silicon carbide.
[edit] Uses in NMR spectroscopy
Tetramethylsilane is used as an internal standard for calibrating chemical shift in 1H, 13C and 29Si NMR spectroscopy. Because all twelve hydrogen atoms in a tetramethylsilane molecule are equivalent, they show up as a singlet peak in a 1H NMR spectrum. The chemical shift of this singlet is assigned as 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 interference 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.
The high volatility of the compound makes it easy to remove it if the compound in the sample is to be recovered and used for further chemistry.
[edit] External links
