Trimethylsilanol (TMS) is an organosilicon compound with the formula (CH3)3SiOH.

[3][4] TMS is a contaminant in the atmospheres of spacecraft, where it arises from the degradation of silicone-based materials.

[5] 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.

[6] 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.

[8] Trimethylsilanol can also be obtained by the basic hydrolysis of hexamethyldisiloxane.

TMS reacts with the silanol groups (R3SiOH) giving silyl ethers.

The compound forms monoclinic crystals.

[2] The vapor pressure function according to Antoine is obtained as log10(P/1 bar) = A − B/(T + C) (P in bar, T in K) with A = 5.44591, B = 1767.766 K and C = −44.888 K in a temperature range from 291 K to 358 K.[2] Below the melting point at −4.5 °C,[12] The 1H NMR in CDCl3 shows a singlet at δ=0.14 ppm.

[13] Like other silanols, trimethylsilanol exhibits antimicrobial properties.