Hexamethyldisiloxane

Last updated
Hexamethyldisiloxane
Hmds.png
Hexamethyldisiloxane-3D-balls.png
Names
Preferred IUPAC name
Hexamethyldisiloxane
Other names
  • Bis(trimethylsilyl) ether
  • Bis(trimethylsilyl) oxide
Identifiers
3D model (JSmol)
AbbreviationsHMDSO, (TMS)2O
1736258
ChEBI
ChemSpider
ECHA InfoCard 100.003.176 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 203-492-7
MeSH Hexamethyldisiloxane
PubChem CID
RTECS number
  • JM9237000
UNII
UN number 1993
  • InChI=1S/C6H18OSi2/c1-8(2,3)7-9(4,5)6/h1-6H3 Yes check.svgY
    Key: UQEAIHBTYFGYIE-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C6H18OSi2/c1-8(2,3)7-9(4,5)6/h1-6H3
    Key: UQEAIHBTYFGYIE-UHFFFAOYAL
  • O([Si](C)(C)C)[Si](C)(C)C
Properties
C6H18OSi2
Molar mass 162.379 g·mol−1
AppearanceColourless liquid
Density 0.764 g·cm−3
Melting point −59 °C (−74 °F; 214 K)
Boiling point 100 to 101 °C (212 to 214 °F; 373 to 374 K)
930.7±33.7  ppb (23 °C) [1]
Vapor pressure 43 hPa (20 °C) [2]
1.377
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
  • Highly flammable liquid and vapour
  • Causes serious eye irritation
GHS labelling:
GHS-pictogram-flamme.svg GHS-pictogram-pollu.svg [2]
Danger [2]
H225, H410 [2]
P210, P233, P240, P273, P403+P235 [2]
NFPA 704 (fire diamond)
NFPA 704.svgHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
4
0
Flash point −1(1) °C
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Hexamethyldisiloxane (HMDSO or MM) is an organosilicon compound with the formula O[Si(CH3)3]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. The molecule is the protypical disiloxane and resembles a subunit of polydimethylsiloxane.

Contents

Synthesis and reactions

Hexamethyldisiloxane can be produced by addition of trimethylsilyl chloride to purified water:

2 Me3SiCl + H2O → 2 HCl + O[Si(CH3)3]2

It also results from the hydrolysis of silylethers and other silyl-protected functional groups. HMDSO can be converted back to the chloride by reaction with Me2SiCl2. [3]

Hexamethyldisiloxane is mainly used as source of the trimethylsilyl 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. [4]

It reacts with rhenium(VII) oxide to give a siloxide: [5]

Re2O7 + O[Si(CH3)3]2 → 2 O3ReOSi(CH3)3

Niche uses

HMDSO is used as an internal standard for calibrating chemical shift in1 H 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.

HMDSO has even poorer solvating power than alkanes. It is therefore sometimes employed to crystallize highly lipophilic compounds.

It is used in liquid bandages (spray on plasters) such as cavilon spray, to protect damaged skin from irritation from other bodily fluids. It is also used to soften and remove adhesive residues left by medical tape and bandages, without causing further skin irritation.

HMDSO is being studied for making low-k dielectric materials for the semi-conductor industries by plasma-enhanced chemical vapor deposition (PECVD).

HMDSO has been used as a reporter molecule to measure tissue oxygen tension (pO2). HMDSO is highly hydrophobic and exhibits high gas solubility, and hence strong nuclear magnetic resonance spin lattice relaxation rate (R1) response to changes in pO2. Molecular symmetry provides a single NMR signal. Following direct injection into tissues it has been used to generate maps of tumor and muscle oxygenation dynamics with respect to hyperoxic gas breathing challenge. [6]

Related Research Articles

<span class="mw-page-title-main">Titanium tetrachloride</span> Inorganic chemical compound

Titanium tetrachloride is the inorganic compound with the formula TiCl4. It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. TiCl4 is a volatile liquid. Upon contact with humid air, it forms thick clouds of titanium dioxide and hydrochloric acid, a reaction that was formerly exploited for use in smoke machines. It is sometimes referred to as "tickle" or "tickle 4", as a phonetic representation of the symbols of its molecular formula.

<span class="mw-page-title-main">Trimethylsilyl group</span> Functional group

A trimethylsilyl group (abbreviated TMS) is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon 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 it useful in a number of applications.

<span class="mw-page-title-main">Sodium bis(trimethylsilyl)amide</span> Chemical compound

Sodium bis(trimethylsilyl)amide is the organosilicon compound with the formula NaN(Si 3)2. This species, usually called NaHMDS, is a strong base used for deprotonation reactions or base-catalyzed reactions. Its advantages are that it is commercially available as a solid and it is soluble not only in ethers, such as THF or diethyl ether, but also in aromatic solvents, like benzene and toluene by virtue of the lipophilic TMS groups.

<span class="mw-page-title-main">Trimethylsilyl chloride</span> Organosilicon compound with the formula (CH3)3SiCl

Trimethylsilyl chloride, also known as chlorotrimethylsilane is an organosilicon compound, with the formula (CH3)3SiCl, often abbreviated Me3SiCl or TMSCl. It is a colourless volatile liquid that is stable in the absence of water. It is widely used in organic chemistry.

<span class="mw-page-title-main">Organosilicon chemistry</span> Organometallic compound containing carbon–silicon bonds

Organosilicon chemistry is the study of organometallic compounds containing carbon–silicon bonds, to which they are called organosilicon compounds. Most organosilicon compounds are similar to the ordinary organic compounds, being colourless, flammable, hydrophobic, and stable to air. Silicon carbide is an inorganic compound.

<span class="mw-page-title-main">Trimethylsilyl cyanide</span> Chemical compound

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 cyanide. It is prepared by the reaction of lithium cyanide and trimethylsilyl chloride:

Bis(trimethylsilyl)amine (also known as hexamethyldisilazane and HMDS) is an organosilicon compound with the molecular formula [(CH3)3Si]2NH. The molecule is a derivative of ammonia with trimethylsilyl groups in place of two hydrogen atoms. An electron diffraction study shows that silicon-nitrogen bond length (173.5 pm) and Si-N-Si bond angle (125.5°) to be similar to disilazane (in which methyl groups are replaced by hydrogen atoms) suggesting that steric factors are not a factor in regulating angles in this case. This colorless liquid is a reagent and a precursor to bases that are popular in organic synthesis and organometallic chemistry. Additionally, HMDS is also increasingly used as molecular precursor in chemical vapor deposition techniques to deposit silicon carbonitride thin films or coatings.

<span class="mw-page-title-main">Hexamethyldisilane</span> Chemical compound

Hexamethyldisilane (TMS2) is the organosilicon compound with the formula Si2(CH3)6, abbreviated Si2Me6. It is a colourless liquid, soluble in organic solvents.

<span class="mw-page-title-main">Lithium bis(trimethylsilyl)amide</span> Chemical compound

Lithium bis(trimethylsilyl)amide is a lithiated organosilicon compound with the formula LiN(Si(CH3)3)2. It is commonly abbreviated as LiHMDS or Li(HMDS) (lithium hexamethyldisilazide - a reference to its conjugate acid HMDS) and is primarily used as a strong non-nucleophilic base and as a ligand. Like many lithium reagents, it has a tendency to aggregate and will form a cyclic trimer in the absence of coordinating species.

Trimethylsilanol (TMS) is an organosilicon compound with the formula (CH3)3SiOH. The Si centre bears three methyl groups and one hydroxyl group. It is a colourless volatile liquid.

<span class="mw-page-title-main">Trimethylsilyl trifluoromethanesulfonate</span> Chemical compound

Trimethylsilyl trifluoromethanesulfonate (TMSOTf) is an organosilicon compound with the formula (CH3)3SiO3SCF3. It is a colorless moisture-sensitive liquid. It is the trifluoromethanesulfonate derivative of trimethylsilyl. It is mainly used to activate ketones and aldehydes in organic synthesis.

<span class="mw-page-title-main">Bis(trimethylsilyl)acetamide</span> Chemical compound

Bis(trimethylsilyl)acetamide (BSA) is an organosilicon compound with the formula MeC(OSiMe3)NSiMe3 (Me = CH3). It is a colorless liquid that is soluble in diverse organic solvents, but reacts rapidly with moisture and solvents containing OH and NH groups. It is used in analytical chemistry to increase the volatility of analytes, e.g., for gas chromatography. It is also used to introduce the trimethylsilyl protecting group in organic synthesis. A related reagent is N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA).

Silylation is the introduction of one or more (usually) substituted silyl groups (R3Si) to a molecule. Silylations are core methods for production of organosilicon chemistry. Silanization involves similar methods but usually refers to attachment of silyl groups to solids.

<span class="mw-page-title-main">Trifluoromethyltrimethylsilane</span> Chemical compound

Trifluoromethyltrimethylsilane (known as Ruppert-Prakash reagent, TMSCF3) is an organosilicon compound with the formula CF3Si(CH3)3. It is a colorless liquid. The compound is a reagent used in organic chemistry for the introduction of the trifluoromethyl group. The compound was first prepared in 1984 by Ingo Ruppert and further developed as a reagent by G. K. Surya Prakash.

<span class="mw-page-title-main">Trimethylsilylacetylene</span> Chemical compound

Trimethylsilylacetylene is the organosilicon compound with the formula (CH3)3SiC2H. A colorless liquid, "tms acetylene", as it is also called, is used as a source of "HC2−" in organic synthesis.

<span class="mw-page-title-main">Metal bis(trimethylsilyl)amides</span>

Metal bis(trimethylsilyl)amides are coordination complexes composed of a cationic metal M with anionic bis(trimethylsilyl)amide ligands (the −N 2 monovalent anion, or −N 2 monovalent group, and are part of a broader category of metal amides.

<span class="mw-page-title-main">Trimethylsilyl iodide</span> Chemical compound

Trimethylsilyl iodide (iodotrimethylsilane or TMSI) is an organosilicon compound with the chemical formula (CH3)3SiI. It is a colorless, volatile liquid at room temperature.

<span class="mw-page-title-main">Trimethylsilyl cyclopentadiene</span> Chemical compound

Trimethylsilyl cyclopentadiene is an organosilicon compound with the chemical formula C5H5Si(CH3)3. It exists as a colorless liquid. It is used in the synthesis of some metal cyclopentadienyl complexes and has attracted interest for its fluxional structure.

<span class="mw-page-title-main">Bis(trimethylsilyl)peroxide</span> Chemical compound

Bis(trimethylsilyl)peroxide (sometimes abbreviated as BTSP) is an organosilicon compound with the formula ((CH3)3SiO)2. It is a colorless liquid that is soluble in organic solvents so long as they lack acidic groups. The compound represents an aprotic analogue of hydrogen peroxide and as such it is used for certain sensitive organic oxidations. Upon treatment with organolithium compounds, it affords the silyl ether.

<span class="mw-page-title-main">(Trimethylsilyl)methyl chloride</span> Chemical compound

(Trimethylsilyl)methyl chloride is the organosilicon compound with the formula (CH3)3SiCH2Cl. A colorless, volatile liquid, it is an alkylating agent that is employed in organic synthesis, especially as a precursor to (trimethylsilyl)methyllithium. In the presence of triphenylphosphine, it olefinates benzophenones:

References

  1. ↑ Sudarsanan Varaprath; Cecil L. Frye; Jerry Hamelink (1996). "Aqueous solubility of permethylsiloxanes (silicones)". Environmental Toxicology and Chemistry . 15 (8): 1263–1265. doi:10.1002/etc.5620150803.
  2. 1 2 3 4 5 Record of Hexamethyldisiloxane in the GESTIS Substance Database of the Institute for Occupational Safety and Health, accessed on November 10, 2021.
  3. ↑ Röshe, L.; John, P.; Reitmeier, R. “Organic Silicon Compounds” Ullmann’s Encyclopedia of Industrial Chemistry. John Wiley and Sons: San Francisco, 2003. doi : 10.1002/14356007.a24_021.
  4. ↑ Pfeifer, J. "Hexamethyldisiloxane" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi : 10.1002/047084289X.
  5. ↑ Schmidt, M.; Schmidbaur, H., "Trimethylsilyl perrhenate", Inorg. Synth. 1967, 9, 149-151. doi : 10.1002/9780470132401.ch40
  6. ↑ Kodibagkar VD, Cui W, Merritt ME, Mason RP. A novel 1H NMR approach to quantitative tissue oximetry using hexamethyldisiloxane. Magn Reson Med 2006;55:743–748 and Kodibagkar VD, Wang X, Pacheco-Torres J, Gulaka P, Mason RP. Proton Imaging of Siloxanes to map Tissue Oxygenation Levels (PISTOL): a tool for quantitative tissue oximetry. NMRBiomed 2008;21:899-907.
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