Trimethylsilyl

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Trimethylsilyl

For tetramethylsilane which also abbreviated as TMS see tetramethylsilane
Tetramethylsilane

Tetramethylsilane is the chemical compound with the chemical formula Si4 or SiMe4 . It is the simplest tetraorganosilane....
.

A trimethylsilyl group (abbreviated TMS) is a functional group

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
in organic chemistry

Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
. This group consists of three methyl groups bonded to a silicon

Silicon

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A trimethylsilyl group (abbreviated TMS) is a functional group

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
in organic chemistry

Organic chemistry

Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
atom [−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 them useful in a number of applications.

A trimethylsilyl group bonded to a methyl group forms tetramethylsilane

Tetramethylsilane

Tetramethylsilane is the chemical compound with the chemical formula Si4 or SiMe4 . It is the simplest tetraorganosilane....
, which is abbreviated as TMS as well.

Compounds with trimethylsilyl groups are not normally found in nature. Chemists sometimes use a trimethylsilylating reagent

Reagent

A reagent or reactant is a substance or compound consumed during a chemical reaction. Solvents and catalysts, although they are involved in the reaction, are usually not referred to as reactants....
to derivatize rather non-volatile compounds such as certain alcohol

Alcohol

In chemistry, an alcohol is any organic compound in which a hydroxyl Functional group is bound to a carbon atom of an alkyl or substituted alkyl group....
s, phenols

Phenols

In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl Functional group attached to an aromatic hydrocarbon group....
, or carboxylic acid

Carboxylic acid

Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the Chemical formula -COH, usually written -COOH or -CO2H....
s by substituting a trimethylsilyl group for a hydrogen in the hydroxyl groups on the compounds. This way trimethylsiloxy

Silyl ether

Silyl ethers are a group of chemical compounds which contain a silicon atom covalent bond to an alkoxy group. The general structure is R1R2R3Si-O-R4 where R4 is an alkyl group or an aryl group....
groups [−O-Si(CH₃)₃] are formed on the molecule. 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

Mass spectrometry is an analytical technique for the determination of the elemental composition of a sample or molecule. It is also used for elucidating the chemical structures of molecules, such as peptides and other chemical compounds....
. Such derivatizations are often done on a small scale in special vials.

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

Protecting group

A protecting group or protective group is introduced into a molecule by chemical modification of a functional group in order to obtain chemoselectivity in a subsequent chemical reaction....
s during chemical synthesis

Chemical synthesis

In chemistry, chemical synthesis is purposeful execution of chemical reactions in order to get a product , or several products. This happens by physics and chemical manipulations usually involving one or more reactions....
or some other chemical reaction

Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
s.

In an NMR spectrum

NMR spectroscopy

Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is the name given to a technique which exploits the magnetic properties of certain nuclei....
, 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

Stopcock

A stopcock is a valve used to restrict or isolate the flow of a liquid or gas through a pipe .In Great Britain a stopcock, not to be confused with a gate valve or a DiCiaccio branch, is used to prevent flow of water into a domestic water system....
" grease

Grease (lubricant)

The term grease is used to describe a number of Quasi-solid lubricants possessing a higher initial viscosity than oil. Although the word grease is also used to describe Rendering fat of animals, in the context of lubricants, it typically applies to a material consisting of a calcium, sodium or lithium soap base emulsion with mineral oi...
, 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

Tetrahedrane is a platonic hydrocarbon with chemical formula 44 and a tetrahedron structure. Extreme angle strain prevents this molecule from forming outside of man-made production....
s.

Super silyl groups

Related to trimethylsiliyl groups are so-called 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 it surpasses the related TIPS group (around 2) and one potential application is its use as a temporary substituent promoting asymmetric induction

Asymmetric induction

Asymmetric induction in stereochemistry describes the preferential formation in a chemical reaction of one enantiomer or diastereoisomer over the other as a result of the influence of a optical isomerism feature present in the Substrate , reagent, catalyst or environment....
for example in this diastereoselective one-pot reaction involving two sequential Mukaiyama aldol reactions :

Trimethylsilyl

Super silyl groups

See also