Tetramethylsilane

Structural formula
General
Surname	Tetramethylsilane
other names	TMS; Silicon tetramethyl;
Molecular formula	C 4 H 12 Si
Brief description	colorless liquid with a characteristic odor
External identifiers / databases
EC number	200-899-1
ECHA InfoCard	100,000,818
PubChem	6396
Wikidata	Q415329
properties
Molar mass	88.23 g mol −1
Physical state	liquid
density	0.65 g cm −3
Melting point	−102 ° C (α-TMS)
boiling point	26 ° C
Vapor pressure	750 h Pa (20 ° C)
solubility	almost insoluble in water (20 mg l −1 at 25 ° C)
Refractive index	1.3587 (20 ° C)
safety instructions
GHS labeling of hazardous substances danger
H and P phrases	H: 224
	P: 210
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Tetramethylsilane , with the constitutional formula Si (CH ₃ ) ₄ , (TMS) is a chemical substance that consists of a central silicon atom (Si) and four methyl groups (–CH ₃ ) attached to it . TMS is largely chemically inert .

presentation

Tetramethylsilane can be synthesized from silicon tetrachloride and methyl magnesium chloride by the Grignard reaction . It can also be prepared by reacting chlorotrimethylsilane with sodium methylaluminum chloride.

{\ displaystyle \ mathrm {3 \ NaCl + AlCl_ {3} +2 \ Al + 3 \ CH_ {3} Cl \ longrightarrow 3 \ NaCH_ {3} AlCl_ {3}}}

{\ displaystyle \ mathrm {NaCH_ {3} AlCl_ {3} + (CH_ {3}) _ {3} SiCl \ longrightarrow (CH_ {3}) _ {4} Si + NaAlCl_ {4}}}

One of the first syntheses of tetramethylsilane was achieved in 1865 by James Mason Crafts and Charles Friedel by reacting silicon tetrachloride with dimethylzinc at 200 ° C.

{\ displaystyle \ mathrm {SiCl_ {4} +2 \ Zn (CH_ {3}) _ {2} \ longrightarrow Si (CH_ {3}) _ {4} +2 \ ZnCl_ {2}}}

use

As a reference in NMR spectroscopy

TMS is used in NMR spectroscopy as a standard substance for calibrating the chemical shift of ¹ H and ¹³ C spectra in organic solvents. A chemical shift of 0 ppm is assigned to the TMS signal. It is particularly well suited for this purpose for the following reasons:

TMS delivers a single intense signal in each of the two spectra.
Because of the low electronegativity of silicon, the signal is at a lower frequency than the signals of ordinary organic compounds .
TMS is largely chemically inert and can therefore be added to the sample as an internal standard.
TMS is highly volatile and can therefore be easily removed again after the measurement.

Alternatives

In aqueous solutions in which TMS is practically insoluble, the water-soluble derivatives DSS (2,2-dimethyl-2-silapentane-5-sulfonic acid, sodium salt) or TSP (3- (trimethylsilyl) -propionic acid, sodium salt) are used instead. In organic solvents, octamethylcyclotetrasiloxane (OMS) can be used as an alternative to TMS if a higher boiling point is desired.

As a methylating agent

Although - as stated above - TMS is largely inert, it has been used successfully as a methylating agent in transmetalation reactions :

{\ displaystyle \ mathrm {(CH_ {3}) _ {4} Si + GaCl_ {3} \ longrightarrow (CH_ {3}) _ {3} SiCl + GaCl_ {2} (CH_ {3})}}

safety instructions

The vapors are irritating to the eyes and the respiratory tract, in higher concentrations there is a narcotic effect.

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h Entry on tetramethylsilane in the GESTIS substance database of the IFA , accessed on February 17, 2017(JavaScript required) .

↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-480.

↑ Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , p. 705.

↑ JM Crafts, C. Friedel: Ueber das Siliciummethyl und die Kieselsäure-Methylather . In: Annals of Chemistry and Pharmacy . tape 136 , no. 2 , 1865, p. 203-211 , doi : 10.1002 / jlac.18651360217 .

↑ H. Schmidbaur, W. Findeiss: A Simple Route to Organogallium Compounds . In: Angewandte Chemie International Edition in English . tape 3 , no. October 10 , 1964, p. 696 , doi : 10.1002 / anie.196406961 .

Web links

Commons : Tetramethylsilane - Collection of pictures, videos and audio files

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h Entry on tetramethylsilane in the GESTIS substance database of the IFA , accessed on February 17, 2017(JavaScript required) .

[CRC90_3_480-2] David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-480.

[brauer-3] Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume I, Ferdinand Enke, Stuttgart 1975, ISBN 3-432-02328-6 , p. 705.

[DOI10.1002/jlac.18651360217-4] JM Crafts, C. Friedel: Ueber das Siliciummethyl und die Kieselsäure-Methylather . In: Annals of Chemistry and Pharmacy . tape 136 , no. 2 , 1865, p. 203-211 , doi : 10.1002 / jlac.18651360217 .