A trimethylsilyl group (abbreviated TMS) is a

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...

organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J ...

. This group consists of three

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ...

groups bonded to a

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...

atom minus;Si(CH₃)₃ which is in turn bonded to the rest of a molecule. This structural group is characterized by chemical inertness and a large molecular volume, which makes it useful in a number of applications. A trimethylsilyl group bonded to a methyl group forms tetramethylsilane, which is abbreviated as TMS as well. Compounds with trimethylsilyl groups are not normally found in nature. Chemists sometimes use a trimethylsilylating reagent to derivatize rather non-volatile compounds such as certain alcohols, phenols, or

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxyli ...

s by substituting a trimethylsilyl group for a hydrogen in the

hydroxyl group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

s on the compounds. This way trimethylsiloxy groups minus;O-Si(CH₃)₃are formed on the molecule. A couple of examples of trimethylsilylating agents include trimethylsilyl chloride and bis(trimethylsilyl)acetamide. Trimethylsilyl groups on a molecule have a tendency to make it more volatile, often making the compounds more amenable to analysis by gas chromatography or

mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a '' mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is u ...

. An example of such trimethylsilylation is mentioned in the

Brassicasterol Brassicasterol (24-methyl cholest-5,22-dien-3β-ol) is a 28- carbon sterol synthesised by several unicellular algae ( phytoplankton) and some terrestrial plants, like rape. This compound has frequently been used as a biomarker for the presence of ...

article. Such derivatizations are often done on a small scale in special

vial A vial (also known as a phial or flacon) is a small glass or plastic vessel or bottle, often used to store medication as liquids, powders or capsules. They can also be used as scientific sample vessels; for instance, in autosampler devices i ...

s. When attached to certain functional groups in a reactant molecule, trimethylsilyl groups may also be used as temporary protecting groups during

chemical synthesis As a topic of chemistry, chemical synthesis (or combination) is the artificial execution of chemical reactions to obtain one or several products. This occurs by physical and chemical manipulations usually involving one or more reactions. In mod ...

or some other

chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking ...

s. In chromatography, derivitization of accessible silanol groups in a bonded stationary phase with trimethylsilyl groups is referred to as endcapping. In an

NMR spectrum Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fiel ...

, signals from atoms in trimethylsilyl groups in compounds will commonly have chemical shifts close to the tetramethylsilane reference peak at 0 ppm. Also compounds, such as high temperature silicone " stopcock" grease, which have polysiloxanes (often called silicones) in them will commonly show peaks from their methyl groups (attached to the silicon atoms) having NMR chemical shifts close to the tetramethylsilane standard peak, such as at 0.07 ppm in CDCl₃. Otherwise very reactive molecules can be isolated when enveloped by bulky trimethylsilyl groups. This effect can be observed in

tetrahedrane Tetrahedrane is a hypothetical platonic hydrocarbon with chemical formula and a tetrahedral structure. The molecule would be subject to considerable angle strain and has not been synthesized as of 2021. However, a number of derivatives have b ...

Super silyl groups

Related to trimethylsilyl groups are "super" silyl groups of which there exist two varieties: A silicon group connected to three trimethylsilyl groups makes a tri(trimethylsilyl)silyl group (TTMSS or TMS₃Si) and a silicon group connected to three tert-butyl groups. The TTMSS group was proposed in 1993 by Hans Bock. With a van der Waals volume of up to 7 cubic

angstrom The angstromEntry "angstrom" in the Oxford online dictionary. Retrieved on 2019-03-02 from https://en.oxforddictionaries.com/definition/angstrom.Entry "angstrom" in the Merriam-Webster online dictionary. Retrieved on 2019-03-02 from https://www.m ...

it surpasses the related TIPS group (around 2) and one potential application is its use as a temporary substituent promoting

asymmetric induction In stereochemistry, asymmetric induction (also enantioinduction) describes the preferential formation in a chemical reaction of one enantiomer or diastereoisomer over the other as a result of the influence of a chiral feature present in the su ...

for example in this diastereoselective one-pot reaction involving two sequential Mukaiyama aldol reactions: : Supersilylapplication

TTMSS can also stand for tris(trimethylsilyl)silane, which is comparable as a chemical reagent to tributyltin hydride without the associated toxicity concern of organotin and

tributyltin Tributyltin (TBT) is an umbrella term for a class of organotin compounds which contain the (C4H9)3 Sn group, with a prominent example being tributyltin oxide. For 40 years TBT was used as a biocide in anti-fouling paint, commonly known as bott ...

compounds. The reagent is employed in radical reductions, hydrosilylation and

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