Hexamethyldisiloxane
Encyclopedia
Hexamethyldisiloxane is a organosilicon compound with the formula O[Si(CH3)3]2. This volatile liquid is used as a solvent
and as a reagent in organic synthesis
. It is prepared by the hydrolysis
of trimethylsilyl chloride
. The molecule is the protypical silyl ether and resembles a subunit of polydimethylsiloxane
.
functional group
(-Si(CH3)3) in organic synthesis
. For example, in the presence of acid catalyst, it converts alcohols and carboxylic acids into the silyl ethers and silyl esters, respectively.
HMDS is used as an internal standard for calibrating chemical shift
in1H
NMR spectroscopy
. It is more easily handled since it is less volatile than the usual standard tetramethylsilane
but still displays only a singlet near 0 ppm.
HMDS has even poorer solvating power than alkanes. It is therefore sometimes employed to crystallize highly lipophilic compounds.
It is also used in liquid bandage
s (spray on plasters) such as cavilon spray, to protect damaged skin from irritation from other bodily fluids.
HMDSO is being studied for making low-k dielectric materials for the semi-conductor industries by PECVD (plasma-enhanced chemical vapor deposition
).
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
and as a reagent in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
. It is prepared by the hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
of trimethylsilyl chloride
Trimethylsilyl chloride
Trimethylsilyl chloride, also known as chlorotrimethylsilane is a silyl halide, with a variety of different uses in chemistry. It has the formula 3SiCl, and under standard conditions it is a colourless liquid, which is stable in the absence of water...
. The molecule is the protypical silyl ether and resembles a subunit of polydimethylsiloxane
Polydimethylsiloxane
Polydimethylsiloxane belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, and is particularly known for its unusual rheological properties. PDMS is optically clear, and, in general, is...
.
Uses
Hexamethyldisiloxane is mainly used as source of the trimethylsilylTrimethylsilyl
A trimethylsilyl group is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom [−Si3], which is in turn bonded to the rest of a molecule...
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. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
(-Si(CH3)3) in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
. For example, in the presence of acid catalyst, it converts alcohols and carboxylic acids into the silyl ethers and silyl esters, respectively.
HMDS is used as an internal standard for calibrating chemical shift
Chemical shift
In nuclear magnetic resonance spectroscopy, the chemical shift is the resonant frequency of a nucleus relative to a standard. Often the position and number of chemical shifts are diagnostic of the structure of a molecule...
in1H
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
NMR spectroscopy
NMR spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is a research technique that exploits the magnetic properties of certain atomic nuclei to determine physical and chemical properties of atoms or the molecules in which they are contained...
. It is more easily handled since it is less volatile than the usual standard tetramethylsilane
Tetramethylsilane
Tetramethylsilane is the chemical compound with the formula Si4. It is the simplest tetraorganosilane. Like all silanes, the TMS framework is tetrahedral...
but still displays only a singlet near 0 ppm.
HMDS has even poorer solvating power than alkanes. It is therefore sometimes employed to crystallize highly lipophilic compounds.
It is also used in liquid bandage
Liquid bandage
Liquid bandage is a topical skin treatment for minor cuts and sores that is sold by several companies. The products are mixtures of chemicals which create a polymeric layer which binds to the skin...
s (spray on plasters) such as cavilon spray, to protect damaged skin from irritation from other bodily fluids.
HMDSO is being studied for making low-k dielectric materials for the semi-conductor industries by PECVD (plasma-enhanced chemical vapor deposition
Plasma-enhanced chemical vapor deposition
Plasma-enhanced chemical vapor deposition is a process used to deposit thin films from a gas state to a solid state on a substrate. Chemical reactions are involved in the process, which occur after creation of a plasma of the reacting gases...
).