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:
2 Me3SiCl + H2O → 2 HCl +
O[Si(CH3)3]2
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:
Re2O7 + O[Si(CH3)3]2 → 2
O3ReOSi(CH3)3
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