Trimethylsilyl chloride

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Trimethylsilyl chloride

General
Systematic name	Trimethylsilyl chloride
Other names	Chlorotrimethylsilane TMSCl
Molecular formula	(CH₃)₃SiCl
SMILES	xxxx
Molar mass	108.94 g/mol
Appearance	Colorless liquid, fumes in moist air
CAS number	[75-77-4]
Properties
Density and phase	0.856 g/cm³, liquid
Solubility in water	reacts
Melting point	−40 °C (233.2 K)
Boiling point	57 °C (330.2 K)
Viscosity	xxx P at 20 °C
Structure
Molecular shape	tetrahedral at Si
Dipole moment	xxx D
Hazards
MSDS	External MSDS
EU classification	Flammable (F) Corrosive (C)
NFPA 704	3 3 2 W
R-phrases	R11, R14, R20, R21, R35, R37
S-phrases	S16, S26, S36, S37, S39, S45
Flash point	−28 °C
Autoignition temperature	400 °C
RTECS number	VV2710000
Supplementary data page
Structure & properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related halosilanes	Trimethylsilyl fluoride Trimethylsilyl bromide Trimethylsilyl iodide
	Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references

Trimethylsilyl chloride, also known as chlorotrimethylsilane is a silyl halide, with a variety of different uses in chemistry. It has the formula (CH₃)₃SiCl, and under standard conditions it is a colourless liquid, which is stable in the absence of water. It can be prepared from silicon tetrachloride by nucleophillic substitution of three of the chloride groups with a nucleophillic methyl source such as methyllithium, however the compound is readily available commercially.

[edit] Uses

Trimethylsilyl chloride has variety of uses in chemistry, both as a source of the trimethylsilyl group, and as an anhydrous source of chloride. Functional groups such as alcohols and amines readily undergo reaction with trimethylsilyl chloride, giving trimethylsilyl ethers and trimethylsilyl amines. These new groups can be used as protecting groups for the original functional group, however the lability of the trimethylsilyl group restricts their utility. The trimethylsilylation can also be used to increase a compounds volatility, enabling gas chromatography of normally non-volatile substances such as glucose. Trimethylsilyl chloride also reacts with metal acetylides to give trimethylsilyl alkynes, which are useful protected forms of alkynes.

The reaction of trimethylsilyl chloride with alcohols gives rise to an equivalent of hydrogen chloride. This reaction can be exploited to create anhydrous solutions of hydrochloric acid in alcohols, which find use in the mild synthesis of esters and acetals from carboxylic acids and ketones respectively.

In the presence of triethylamine and lithium diisopropylamide, enolisable aldehydes, ketones and esters are converted to trimethylsilyl enol ethers. Despite their inherent instability, these compounds have found wide application in organic chemistry; oxidation of the double bond by epoxidation or dihydroxylation can be used to return the original carbonyl group with an alcohol group at the alpha carbon. The trimethylsilyl enol ethers can also be used as masked enolate equivalents in the Mukaiyama aldol addition.