Tetramethylsilane

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Tetramethylsilane
Flat structural formula
Ball-and-stick model Space-filling model
Identifiers
Abbreviations TMS
CAS number 75-76-3 YesY
PubChem 6396
ChemSpider 6156 YesY
EC number 200-899-1
UN number 2749
MeSH Tetramethylsilane
ChEBI CHEBI:203731 N
ChEMBL CHEMBL68073 YesY
RTECS number VV5705400
Beilstein Reference 1696908
Jmol-3D images Image 1
Properties
Molecular formula C4H12Si
Molar mass 88.22 g mol−1
Appearance Colourless liquid
Density 0.648 g cm-3
Melting point −99 °C (−146 °F; 174 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
EU classification Extremely Flammable F+
R-phrases R12
S-phrases S16, S3/7, S33, S45
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propane Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point -28-(-27) °C
Related compounds
Related silanes Silane

Silicon tetrabromide
Silicon tetrachloride
Silicon tetrafluoride
Silicon tetraiodide
Hexamethyldisilane

Related compounds Neopentane

Tetramethyltin

Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
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 reaction[edit]

TMS is a by-product of the production of methyl chlorosilanes, SiClx(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, 2, and 3.[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.

Uses in NMR spectroscopy[edit]

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.[2]

Because all twelve hydrogen atoms in a tetramethylsilane molecule are equivalent, its 1H NMR spectrum consists of a singlet. [3] 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.

Commercial NMR solvents often are supplied without TMS. 1H NMR spectra can be calibrated against residual protio-solvent (e.g. the remaining 0.001% or so of undeuterated chloroform in commercial CDCl3). As deuterium is not observed in 1H NMR, the residual protio-solvent signals can be observed clearly. For 13C NMR work, spectra are usually calibrated against the deuterated solvent peak. For example, deuterochloroform shows a triplet of equal height at δ 77.0. [5] The triplet is explained by applying the 2nI + 1 rule; for the case of deuterium, I = 1. Tables and charts of chemical shifts for various types of NMR spectroscopy are often provided by vendors of NMR solvents. Work has also been done to prepare comprehensive tables of chemical shifts of solvents and impurities.[6][7]

References[edit]

  1. ^ Elschenbroich, C. ”Organometallics” (2006) Wiley-VCH: Weinheim. ISBN 978-3-527-29390-2
  2. ^ Jerry R. Mohrig, Christina Noring Hammond, Paul F. Schatz (January 2006). Techniques in Organic Chemistry (Google Books excerpt). pp. 273–274. ISBN 978-0-7167-6935-4. 
  3. ^ The Theory of NMR - Chemical Shift
  4. ^ The Theory of NMR - Chemical Shift
  5. ^ The Theory of NMR - Solvents for NMR spectroscopy
  6. ^ Gottlieb, Hugo E.; Kotlyar, Vadim; Nudelman, Abraham (1997). "NMR Chemical Shifts of Common Laboratory Solvents as Trace Impurities". The Journal of Organic Chemistry 62 (21): 7512–7515. doi:10.1021/jo971176v. PMID 11671879. 
  7. ^ Fulmer, Gregory R.; Miller, Alexander J. M.; Sherden, Nathaniel H.; Gottlieb, Hugo E.; Nudelman, Abraham; Stoltz, Brian M.; Bercaw, John E.; Goldberg, Karen I. (2010). "NMR Chemical Shifts of Trace Impurities: Common Laboratory Solvents, Organics, and Gases in Deuterated Solvents Relevant to the Organometallic Chemist". Organometallics 29: 2176. doi:10.1021/om100106e.