Hexamethyldisiloxane

Hexamethyldisiloxane
Names
	IUPAC name Hexamethyldisiloxane
	Other names HMDS; HMDSO; (TMS)2O; Bis(trimethylsilyl) ether; Bis(trimethylsilyl) oxide
Identifiers
CAS Number	107-46-0 ;
3D model (JSmol)	Interactive image;
ECHA InfoCard	100.003.176
RTECS number	JM9237000;
CompTox Dashboard (EPA)	DTXSID4026769 ;
	SMILES CSi(C)(C)OSi(C)(C)C;
Properties
Chemical formula	C6H18OSi2
Molar mass	162.38 g/mol
Appearance	colorless liquid
Density	0.764 g/cm3
Melting point	−59 °C
Boiling point	101 °C
Solubility in water	low
Solubility in other solvents	all organic solvents
Refractive index (nD)	1.377
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	flammable
Related compounds
	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

Hexamethyldisiloxane is a chemical compound with the formula O[Si(CH₃)₃]₂. This volatile liquid is used as a solvent and as a reagent. The species arises by the hydrolysis of trimethylsilyl chloride. The molecule is the protypical silyl ether and can be considered a subunit of polydimethylsiloxane.

Uses

It is primarily 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) like in cavilon spray used on the body 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.

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

[1]