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IUPAC name Hexamethyldisiloxane
Other names HMDS
Bis(trimethylsilyl) ether
Bis(trimethylsilyl) oxide
CAS number 107-46-0
RTECS number JM9237000
Molecular formula C6H12OSi2
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
Main hazards flammable
R-phrases 11
S-phrases 16
Related Compounds
Related compounds Tetramethylsilane
Dimethyl ether
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and 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.


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


Like most siloxanes, hexamethyldisiloxane is fairly innocuous.


  1. ^ Pfeifer, J. "Hexamethyldisiloxane" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Hexamethyldisiloxane". A list of authors is available in Wikipedia.
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