Hexamethyldisiloxane

Chembox new
Name = Hexamethyldisiloxane
ImageFile = Hmds.png ImageName =
IUPACName = Hexamethyldisiloxane
OtherNames = HMDS
HMDSO
Bis(trimethylsilyl) ether
Bis(trimethylsilyl) oxide
Section1 = Chembox Identifiers
SMILES = CSi(C)(C)OSi(C)(C)C
CASNo = 107-46-0
RTECS = JM9237000
Section2 = Chembox Properties
Formula = C₆H₁₈OSi₂
MolarMass = 162.38 g/mol
Appearance = colorless liquid
Density = 0.764 g/cm³
Solubility = low
Solvent = other solvents
SolubleOther = all organic solvents
MeltingPt = −59 °C
BoilingPt = 101 °C
Viscosity =
RefractIndex = 1.377
Section3 = Chembox Structure
Dipole =
Section7 = Chembox Hazards
ExternalMSDS =
MainHazards = flammable
FlashPt =
RPhrases = 11
SPhrases = 16
Section8 = Chembox Related
OtherCpds = Tetramethylsilane
Dimethyl ether
Bis(trimethylsilyl)amine

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

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.

afety

Like most siloxanes, hexamethyldisiloxane is fairly innocuous.

References