trimetyylisilyyliryhmä

The trimethylsilyl group, often abbreviated as TMS, is a functional group with the chemical formula (CH₃)₃Si–. It consists of a silicon atom bonded to three methyl groups and one other atom or group. This group is widely used in organic chemistry and biochemistry as a protecting group for alcohols, amines, and other functional groups. Its bulky nature can provide steric hindrance, influencing the reactivity and selectivity of chemical reactions.

The trimethylsilyl group is highly lipophilic, meaning it dissolves well in nonpolar solvents. This property makes it useful for increasing the solubility of polar compounds in organic media, which can aid in their purification or analysis by techniques like chromatography or mass spectrometry. The Si–O bond in silyl ethers, formed when TMS protects an alcohol, is relatively weak and can be easily cleaved under acidic or basic conditions, or with fluoride ions, regenerating the original alcohol. This reversibility is key to its utility as a protecting group.

In analytical chemistry, the trimethylsilyl group is frequently introduced to increase the volatility and thermal stability of molecules, making them amenable to gas chromatography (GC). For example, derivatization of sugars or steroids with TMS reagents is a common practice. The characteristic signals of the three methyl groups in the ¹H NMR spectrum and the presence of the silicon atom in ¹³C and ²⁹Si NMR spectra also make the TMS group easily identifiable.