Hexamethyldisiloxane

Hexamethyldisiloxane

Names
Preferred IUPAC name Hexamethyldisiloxane
Other names Bis(trimethylsilyl) ether Bis(trimethylsilyl) oxide
Identifiers
CAS Number	107-46-0 Y
3D model (JSmol)	Interactive image
Abbreviations	HMDSO, (TMS)2O
Beilstein Reference	1736258
ChEBI	CHEBI:78002 N
ChemSpider	23150 Y
ECHA InfoCard	100.003.176
EC Number	203-492-7
MeSH	Hexamethyldisiloxane
PubChem CID	24764
RTECS number	JM9237000
UNII	D7M4659BPU Y
UN number	1993
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
SMILES O([Si](C)(C)C)[Si](C)(C)C
Properties
Chemical formula	C6H18OSi2
Molar mass	162.38 g·mol−1
Appearance	Colourless liquid
Density	0.764 g cm−3
Melting point	−59 °C (−74 °F; 214 K)
Boiling point	100 to 101 °C (212 to 214 °F; 373 to 374 K)
Solubility in water	930.7±33.7 ppb (23 °C)
Vapor pressure	43 hPa (20 °C)
Refractive index (nD)	1.377
Hazards
Main hazards	Highly flammable liquid and vapour Causes serious eye irritation
EU classification (DSD) (outdated)	F
R-phrases (outdated)	R11
S-phrases (outdated)	S16
NFPA 704	4 1 0
Flash point	-1(1) °C
Related compounds
Related compounds	Disiloxane Tetramethylsilane Dimethyl ether Bis(trimethylsilyl)amine Tetrakis(trimethylsilyloxy)silane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Causes serious eye irritation

Tetramethylsilane
Dimethyl ether
Bis(trimethylsilyl)amine Tetrakis(trimethylsilyloxy)silane

Hexamethyldisiloxane (HMDSO) is an organosilicon compound with the formula O[Si(CH₃)₃]₂. This volatile colourless 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 disiloxane and resembles a subunit of polydimethylsiloxane.

Hexamethyldisiloxane can be produced by hydrolysis of trimethylsilyl chloride:

It also results from the hydrolysis of silylethers and other silyl-protected functional groups. HMDSO can be converted back to the chloride by reaction with Me₂SiCl₂.

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.

It reacts with rhenium(VII) oxide to give the silanoate complex:

HMDSO 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.