Hexamethyldisiloxane

Hexamethyldisiloxane

Preferred IUPAC name Hexamethyldisiloxane
Other names Bis(trimethylsilyl) ether Bis(trimethylsilyl) oxide
Identifiers
Abbreviations	HMDSO, (TMS)₂O
CAS number	107-46-0^Y
PubChem	24764
ChemSpider	23150^Y
UNII	D7M4659BPU^Y
EC number	203-492-7
UN number	1993
MeSH	Hexamethyldisiloxane
RTECS number	JM9237000
Beilstein Reference	1736258
Jmol-3D images	Image 1
SMILES O([Si](C)(C)C)[Si](C)(C)C
InChI InChI=1S/C6H18OSi2/c1-8(2,3)7-9(4,5)6/h1-6H3^Y Key: UQEAIHBTYFGYIE-UHFFFAOYSA-N^Y InChI=1/C6H18OSi2/c1-8(2,3)7-9(4,5)6/h1-6H3 Key: UQEAIHBTYFGYIE-UHFFFAOYAL
Properties
Molecular formula	C₆H₁₈OSi₂
Molar mass	162.38 g mol⁻¹
Exact mass	162.089618264 g mol^-1
Appearance	Colourless liquid
Density	0.764 g cm^-3
Melting point	−59 °C, 214 K, -74 °F
Boiling point	100-101 °C, 373-374 K, 212-214 °F
Refractive index (n_D)	1.377
Hazards
EU classification	F
R-phrases	R11
S-phrases	S16
Main hazards	Highly flammable liquid and vapour Causes serious eye irritation
NFPA 704	4 1 0
Flash point	-1(1) °C
Related compounds
Related compounds	Disiloxane Tetramethylsilane Dimethyl ether Bis(trimethylsilyl)amine
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Hexamethyldisiloxane is a organosilicon compound with the formula O[Si(CH₃)₃]₂. This volatile liquid is used as a solvent and as a reagent in organic synthesis. It is prepared by the hydrolysis of trimethylsilyl chloride. The molecule is the protypical silyl ether and resembles a subunit of polydimethylsiloxane.

Uses

Hexamethyldisiloxane is mainly used as source of the trimethylsilyl functional group (-Si(CH₃)₃) in organic synthesis. For example, in the presence of acid catalyst, it converts alcohols and carboxylic acids into the silyl ethers and silyl esters, respectively.^[1]

HMDS is used as an internal standard for calibrating chemical shift in¹H NMR spectroscopy. It is more easily handled since it is less volatile than the usual standard tetramethylsilane but still displays only a singlet near 0 ppm.

HMDS has even poorer solvating power than alkanes. It is therefore sometimes employed to crystallize highly lipophilic compounds.

It is also used in liquid bandages (spray on plasters) such as cavilon spray, to protect damaged skin from irritation from other bodily fluids.

HMDSO is being studied for making low-k dielectric materials for the semi-conductor industries by PECVD (plasma-enhanced chemical vapor deposition).

References

^ Pfeifer, J. "Hexamethyldisiloxane" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289.