Trimethylsilyl chloride, also known as chlorotrimethylsilane is an
organosilicon compound (
silyl halide
Organosilicon compounds are organometallic compounds containing carbon–silicon chemical bond, bonds. Organosilicon chemistry is the corresponding science of their preparation and properties. Most organosilicon compounds are similar to the ordin ...
), with the formula (CH
3)
3SiCl, often abbreviated Me
3SiCl or TMSCl. It is a colourless volatile liquid that is stable in the absence of water. It is widely used in organic chemistry.
Preparation
TMSCl is prepared on a large scale by the ''
direct process The direct process, also called the direct synthesis, Rochow process, and Müller-Rochow process is the most common technology for preparing organosilicon compounds on an industrial scale. It was first reported independently by Eugene G. Rochow and ...
'', the reaction of
methyl chloride
Chloromethane, also called methyl chloride, Refrigerant-40, R-40 or HCC 40, is an organic compound with the chemical formula . One of the haloalkanes, it is a colorless, odorless, flammable gas. Methyl chloride is a crucial reagent in industrial ...
with a silicon-copper alloy. The principal target of this process is
dimethyldichlorosilane
Dimethyldichlorosilane is a tetrahedral, organosilicon compound with the formula Si(CH3)2Cl2. At room temperature it is a colorless liquid that readily reacts with water to form both linear and cyclic Si-O chains. Dimethyldichlorosilane is made ...
, but substantial amounts of the trimethyl and monomethyl products are also obtained.
The relevant reactions are (Me = CH
3):
: x MeCl + Si → Me
3SiCl, Me
2SiCl
2, MeSiCl
3, other products
Typically about 2–4% of the product stream is the monochloride, which forms an
azeotrope with MeSiCl
3.
Reactions and uses
TMSCl is reactive toward nucleophiles, resulting in the replacement of the chloride. In a characteristic reaction of TMSCl, the nucleophile is water, resulting in
hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
to give the
hexamethyldisiloxane
Hexamethyldisiloxane (HMDSO) is an organosilicon compound with the formula O i(CH3)3sub>2. This volatile colourless liquid is used as a solvent and as a reagent in organic synthesis. It is prepared by the hydrolysis of trimethylsilyl chloride. ...
:
:2 Me
3SiCl + H
2O → Me
3Si-O-SiMe
3 + 2 HCl
The related reaction of trimethylsilyl chloride with alcohols can be exploited to produce
anhydrous
A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...
solutions of
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
in alcohols, which find use in the mild synthesis of
ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
s from
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. Carboxylic ...
s and
nitrile
In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix ''cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including met ...
s as well as,
acetals from
ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
s. Similarly, trimethylsilyl chloride is also used to silanize
laboratory glassware, making the surfaces more
lipophilic.
Silylation in organic synthesis
By the process of
silylation, polar functional groups such as
alcohols
In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which is ...
and
amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...
s readily undergo reaction with trimethylsilyl chloride, giving
trimethylsilyl ethers and
trimethylsilyl
A trimethylsilyl group (abbreviated TMS) is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom minus;Si(CH3)3 which is in turn bonded to the rest of a molecule. This structural group is ch ...
amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...
s. These new groups
"protect" the original functional group by removing the labile protons and decreasing the basicity of the heteroatom. The
lability of the Me
3Si-O and Me
3Si-N groups can later be removed ("deprotected").
Trimethylsilyl
A trimethylsilyl group (abbreviated TMS) is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom minus;Si(CH3)3 which is in turn bonded to the rest of a molecule. This structural group is ch ...
ation can also be used to increase the volatility of a compound, enabling
gas chromatography
Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, ...
of normally nonvolatile substances such as
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
.
Trimethylsilyl chloride also reacts with carbanions to give trimethylsilyl derivatives. Lithium acetylides react to give trimethylsilyl
alkynes such as
bis(trimethylsilyl)acetylene. Such derivatives are useful protected forms of alkynes.
In the presence of
triethylamine
Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine or tetraethylammonium, for which TEA ...
and
lithium diisopropylamide,
enol
In organic chemistry, alkenols (shortened to enols) are a type of reactive structure or intermediate in organic chemistry that is represented as an alkene ( olefin) with a hydroxyl group attached to one end of the alkene double bond (). The te ...
isable
aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...
s,
ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
s and
ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
s are converted to
trimethylsilyl
A trimethylsilyl group (abbreviated TMS) is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom minus;Si(CH3)3 which is in turn bonded to the rest of a molecule. This structural group is ch ...
enol ether
In organic chemistry an enol ether is an alkene with an alkoxy substituent. The general structure is R2C=CR-OR where R = H, alkyl or aryl. A common subfamily of enol ethers are vinyl ethers, with the formula ROCH=CH2. Important enol ethers include ...
s. Despite their hydrolytic instability, these compounds have found wide application in organic chemistry;
oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
of the
double bond by
epoxidation or
dihydroxylation
Dihydroxylation is the process by which an alkene is converted into a vicinal diol. Although there are many routes to accomplish this oxidation, the most common and direct processes use a high-oxidation-state transition metal (typically osmium or ...
can be used to return the original
carbonyl group with an
alcohol
Alcohol most commonly refers to:
* Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom
* Alcohol (drug), an intoxicant found in alcoholic drinks
Alcohol may also refer to:
Chemicals
* Ethanol, one of sev ...
group at the alpha carbon. The
trimethylsilyl
A trimethylsilyl group (abbreviated TMS) is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom minus;Si(CH3)3 which is in turn bonded to the rest of a molecule. This structural group is ch ...
enol ether
In organic chemistry an enol ether is an alkene with an alkoxy substituent. The general structure is R2C=CR-OR where R = H, alkyl or aryl. A common subfamily of enol ethers are vinyl ethers, with the formula ROCH=CH2. Important enol ethers include ...
s can also be used as masked
enolate equivalents in the
Mukaiyama aldol addition
The Mukaiyama aldol addition is an organic reaction and a type of aldol reaction between a silyl enol ether and an aldehyde or formate. The reaction was discovered by Teruaki Mukaiyama (1927–2018) in 1973. His choice of reactants allows fo ...
.
Dehydrations
Dehydration of metal chlorides with trimethylsilyl chloride in THF gives the solvate as illustrated by the case of
chromium trichloride:
:CrCl
3 + 12 Me
3SiCl → CrCl
3(THF)
3 + 6 (Me
3Si)
2O + 12 HCl
Other reactions
Trimethylsilyl chloride is used to prepare other trimethylsilyl halides and
pseudohalides, including trimethylsilyl fluoride, trimethylsilyl bromide,
trimethylsilyl iodide
Trimethylsilyl iodide (iodotrimethylsilane or TMSI) is an organosilicon compound with the chemical formula (CH3)3SiI. It is a colorless, volatile liquid at room temperature.
Preparation
Trimethylsilyl iodide may be prepared by the oxidative cleav ...
,
trimethylsilyl cyanide
Trimethylsilyl cyanide is the chemical compound with the formula (CH3)3SiCN. This volatile liquid consists of a cyanide group, that is CN, attached to a trimethylsilyl group. The molecule is used in organic synthesis as the equivalent of hydrogen ...
,
trimethylsilyl azide, and trimethylsilyl trifluoromethanesulfonate (TMSOTf). These compounds are produced by a
salt metathesis reaction between trimethylsilyl chloride and a salt of the (pseudo)halide (MX):
:MX + Me
3Si-Cl → MCl + Me
3Si-X
TMSCl, lithium, and nitrogen molecule react to give
tris(trimethylsilyl)amine
Tris(trimethylsilyl)amine is the simplest tris(trialkylsilyl)amine which are having the general formula (R3Si)3N, in which all three hydrogen atoms of the ammonia are replaced by trimethylsilyl groups (-Si(CH3)3). Tris(trimethylsilyl)amine has bee ...
, under catalysis by
nichrome
Nichrome (also known as NiCr, nickel-chromium or chromium-nickel) is a family of alloys of nickel, chromium, and often iron (and possibly other elements) commonly used as resistance wire, heating elements in devices like toasters, electrical kettl ...
wire or
chromium trichloride:
:3 Me
3SiCl + 3 Li + → (Me
3Si)
3N + 3 LiCl
Using this approach, atmospheric nitrogen can be introduced into organic substrate. For example, tris(trimethylsilyl)amine reacts with α,δ,ω-tri
ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
s to give tricyclic
pyrrole
Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C4 H4 NH. It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., ''N''-meth ...
s.
Reduction of trimethylsilyl chloride give
hexamethyldisilane:
:2 Me
3SiCl + 2 Na → 2 NaCl + Me
3Si-SiMe
3
References
{{DEFAULTSORT:Trimethylsilyl Chloride
Reagents for organic chemistry
Trimethylsilyl compounds
Chlorosilanes