Tetramethylsilane

Tetramethylsilane
Names
	Preferred IUPAC name Tetramethylsilane
Identifiers
CAS Number	75-76-3 ;
3D model (JSmol)	Interactive image;
Abbreviations	TMS
Beilstein Reference	1696908
ChEBI	CHEBI:85361 ;
ChEMBL	ChEMBL68073 ;
ChemSpider	6156 ;
ECHA InfoCard	100.000.818
EC Number	200-899-1;
MeSH	Tetramethylsilane
PubChem CID	6396;
RTECS number	VV5705400;
UNII	41Y0RBG14Q ;
UN number	2749
CompTox Dashboard (EPA)	DTXSID9026423 ;
	InChI InChI=1S/C4H12Si/c1-5(2,3)4/h1-4H3 Key: CZDYPVPMEAXLPK-UHFFFAOYSA-N ;
	SMILES C[Si](C)(C)C;
Properties
Chemical formula	C4H12Si
Molar mass	88.225 g·mol−1
Appearance	Colourless liquid
Density	0.648 g cm−3
Melting point	−99 to −102 °C (−146 to −152 °F; 174 to 171 K)
Boiling point	26 to 28 °C (79 to 82 °F; 299 to 301 K)
Solubility	organic solvents
Structure
Molecular shape	Tetrahedral at carbon and silicon
Dipole moment	0 D
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H224, H302, H411
Precautionary statements	P210, P233, P240, P241, P242, P243, P264, P270, P273, P280, P301+P312, P303+P361+P353, P330, P370+P378, P391, P403+P235, P501
NFPA 704 (fire diamond)	3 4 1
Flash point	−28 to −27 ℃ (–18 to –16 ℉), vapor may be pyrophoric
Related compounds
Related silanes	Silane; Silicon tetrabromide; Silicon tetrachloride; Silicon tetrafluoride; Silicon tetraiodide; Hexamethyldisilane;
Related compounds	Neopentane; Tetramethylgermane; Tetramethyltin; Tetramethyllead;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Tetramethylsilane (abbreviated as TMS) is the organosilicon compound with the formula Si(CH₃)₄. It is the simplest tetraorganosilane. Like all silanes, the TMS framework is tetrahedral. TMS is a building block in organometallic chemistry but also finds use in diverse niche applications.

Synthesis and reactions

TMS is a by-product of the production of methyl chlorosilanes, SiCl_x(CH₃)_4−x, via the direct process of reacting methyl chloride with silicon. The more useful products of this reaction are those for x = 1 (trimethylsilyl chloride), 2 (dimethyldichlorosilane), and 3 (methyltrichlorosilane).^[1]

TMS undergoes deprotonation upon treatment with butyllithium to give (H₃C)₃SiCH₂Li. The latter, trimethylsilylmethyl lithium, is a relatively common alkylating agent.

In chemical vapor deposition, TMS is the precursor to silicon dioxide or silicon carbide, depending on the deposition conditions. In the formation of silicon carbide, carbosilanes, such as 1,3,5,7-tetramethyl-1,3,5,7-tetrasilaadamantane, are observed as intermediates.^[2]

Uses in NMR spectroscopy

Tetramethylsilane is the accepted internal standard for calibrating chemical shift for ¹H, ¹³C and ²⁹Si NMR spectroscopy in organic solvents (where TMS is soluble). In water, where it is not soluble, sodium salts of DSS, 2,2-dimethyl-2-silapentane-5-sulfonate, are used instead. Because of its high volatility, TMS can easily be evaporated, which is convenient for recovery of samples analyzed by NMR spectroscopy.^[3]

Because all twelve hydrogen atoms in a tetramethylsilane molecule are equivalent, its ¹H NMR spectrum consists of a singlet.^[4] The chemical shift of this singlet is assigned as δ 0, and all other chemical shifts are determined relative to it. The majority of compounds studied by ¹H NMR spectroscopy absorb downfield of the TMS signal, thus there is usually no interference between the standard and the sample. Similarly, all four carbon atoms in a tetramethylsilane molecule are equivalent.^[4] In a fully decoupled ¹³C NMR spectrum, the carbon in the tetramethylsilane appears as a singlet, allowing for easy identification. The chemical shift of this singlet is also set to be δ 0 in the ¹³C spectrum, and all other chemical shifts are determined relative to it.

References

^ Elschenbroich, C. (2006). Organometallics. Weinheim: Wiley-VCH. ISBN 978-3-527-29390-2.
^ Fritz, Gerhard; Matern, Eberhard (1986). Carbosilanes. doi:10.1007/978-3-642-70800-8. ISBN 978-3-642-70802-2.
^ Mohrig, Jerry R.; Noring Hammond, Christina; Schatz, Paul F. (January 2006). Techniques in Organic Chemistry (Google Books excerpt). Macmillan. pp. 273–274. ISBN 978-0-7167-6935-4.
^ ^a ^b "The Theory of NMR - Solvents for NMR Spectroscopy". Archived from the original on 2015-01-23. Retrieved 2014-01-23.

[wiley-1] Elschenbroich, C. (2006). Organometallics. Weinheim: Wiley-VCH. ISBN 978-3-527-29390-2.

[2] Fritz, Gerhard; Matern, Eberhard (1986). Carbosilanes. doi:10.1007/978-3-642-70800-8. ISBN 978-3-642-70802-2.

[mohrig-3] Mohrig, Jerry R.; Noring Hammond, Christina; Schatz, Paul F. (January 2006). Techniques in Organic Chemistry (Google Books excerpt). Macmillan. pp. 273–274. ISBN 978-0-7167-6935-4.

[The_Theory_of_NMR_-_Chemical_Shift-4] "The Theory of NMR - Solvents for NMR Spectroscopy". Archived from the original on 2015-01-23. Retrieved 2014-01-23.

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