Trimethylsilanol
Trimethylsilanol is an organosilicon compound with the formula. The Si centre bears three methyl groups and one hydroxyl group. It is a colourless volatile liquid.
Occurrence
TMS is a contaminant in the atmospheres of spacecraft, where it arises from the degradation of silicone-based materials. Specifically, it is the volatile product from the hydrolysis of polydimethylsiloxane, which are generally terminated with trimethylsilyl groups:TMS and related volatile siloxanes are formed by hydrolysis of silicones-based containing materials, which are found in detergents and cosmetic products.
Traces of trimethylsilanol, together with other volatile siloxanes, are present in biogas and landfill gas, again resulting from the degradation of silicones. As their combustion forms particles of silicates and microcrystalline quartz, which cause abrasion of combustion engine parts, they pose problems for the use of such gases in combustion engines.
Production
Trimethylsilanol cannot be produced by simple hydrolysis of chlorotrimethylsilane as this reaction leads to the etherification product hexamethyldisiloxane, because of the by-product hydrochloric acid.Trimethylsilanol is accessible by weakly basic hydrolysis of chlorotrimethylsilane, since the dimerization can thus be avoided. Trimethylsilanol can also be obtained by the basic hydrolysis of hexamethyldisiloxane.
Reactions
Trimethylsilanol is a weak acid with a pKa value of 11. The acidity is comparable to that of orthosilicic acid, but much higher than the one of alcohols like tert-butanol. Deprotonation with sodium hydroxide gives sodium trimethylsiloxide.TMS reacts with the silanols giving silyl ethers.