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Hexamethyldisiloxane

Hexamethyldisiloxane

IUPAC name	Hexamethyldisiloxane
Other names	HMDS HMDSO Bis(trimethylsilyl) ether Bis(trimethylsilyl) oxide
Identifiers
CAS number	107-46-0
RTECS number	JM9237000
SMILES	CSi(C)(C)OSi(C)(C)C
Properties
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 (n_D)	1.377
Hazards
Main hazards	flammable
R-phrases	11
S-phrases	16
Related Compounds
Related compounds	Tetramethylsilane Dimethyl ether Bis(trimethylsilyl)amine
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.

Additional recommended knowledge

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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

Safety

Like most siloxanes, hexamethyldisiloxane is fairly innocuous.

References

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

Category: Organosilicon compounds