Disiloxane

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Disiloxane
Structural formula of disiloxane with explicit hydrogens
Ball-and-stick model of the disiloxane molecule
Names
IUPAC name
Disiloxane
Other names
Disilyl ether

Disilyl oxide
Hexahydrodisiloxane
Perhydrodisiloxane
Silyl ether

Silyl oxide
Identifiers
3D model (JSmol)
Abbreviations DS

DSE
DSO

ChEBI
ChemSpider
1206
MeSH Disiloxane
Properties
H6OSi2
Molar mass 78.22 g·mol−1
Appearance Colorless gas
Melting point 171.26 °C (340.27 °F; 444.41 K)
Boiling point 451.67 °C (845.01 °F; 724.82 K)
0.24 D
Structure
Orthorhombic
Pmm2
Bent
Hazards
Safety data sheet See: data page
NFPA 704
Flammability code 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., propaneHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroformReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calciumSpecial hazards (white): no codeNFPA 704 four-colored diamond
4
2
1
Related compounds
Related compounds
Dimethyl ether

Disilane
Silane
Silanol
Trisilane

Supplementary data page
Refractive index (n),
Dielectric constantr), etc.
Thermodynamic
data
Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Disiloxane has the chemical formula Si
2
H
6
O
. It is the simplest known siloxane with hydrogen only R groups. The molecule contains six equivalent Si-H bonds and two equivalent Si-O bonds. Disiloxane exists as a colorless, pungent gas under standard conditions. However, it is generally safe for human use as evidence in its widespread use in cosmetics. It is also commonly known as disilyl ether, disilyl oxide, and perhydrodisiloxane

Structure[edit]

Disiloxane has a simple structure that consists of a siloxane bond (Si-O-Si) and hydrogen R groups.

The structure of disiloxane has been studied by a variety of spectroscopic methods such as electron diffraction, dipole moment, and nuclear magnetic resonance. Commonly, the bond angles of the Si-O-Si bond are studied due to their unusual nature. These bonds are typically exhibit bond angles that are larger than average, around 130 to 160 degrees, larger bond lengths are not uncommon. Typical bond angles with oxygen atoms are around 105 to 125 degrees corresponding to the hybrid s and p orbitals. The abnormally large bond angle has led some scientists to believe that the molecule exhibits a linear geometry while others have collected data indicating that disiloxane exhibits a bent geometry. This disagreement usually depends on the spectroscopic technique used to analyze the compound. The unusual bond angle may be due to unshared electron interactions from oxygen interacting with the d orbitals of silicon. It has been estimated that the two lone pairs of oxygen are each about 50% involved with π bond interactions with silicon’s d orbitals. There is also evidence of π bonding between the p and d orbitals which results in a bond shortening between Si-O which improves the overlap and overall stability of the molecule. Because of this shortening, the Si-O bonds can exhibit some partial double bond behavior.

In addition to studies of bond angles, vibrational analyses have also been done to determine the symmetry elements of disiloxane. IR and Raman spectroscopy have been used to propose a point group of D3d.

Synthesis[edit]

Synthesis of disiloxane is typically done by taking a hydrosilane species with a substituent leaving group and reacting it with water to produce silanol. The silanol is then reacted with itself to produce the final disiloxane through dehydrogenative coupling. This is shown in the reactions below:

H3SiX + H2O → H3SiOH + HX (first step)

2 H3SiOH → H3SiOSiH3 + H2O (second step)

Other methods of synthesis involve the use of gold on carbon as a catalyst for the reaction carried out in water as well as InBr3- catalyzed oxidation of hydrosilanes.

Uses[edit]

Disiloxanes can be used as sealants for construction, paints, inks, and coatings, cosmetics, mechanical fluids, textile applications, and paper coatings.

Commercial use of disiloxane is common in cosmetics. It is commonly found in products such as sunscreen, moisturizer, hair spray, eye liner, body spray, nail polish, makeup remover, and conditioner. The properties that disiloxane exhibits in these products include fast drying, oil reducing, moisturizing, skin conditioning, and defoaming agent (preventing formation of foam).

Disiloxanes have been approved as teen and child safe. Siloxanes of many kinds are found to be extremely safe for topical use but can be dangerous if ingested.

Variations[edit]

The term disiloxane is commonly used to refer to structures that exhibit much more complex R groups than hydrogen. The most common molecule that makes use of this naming is Hexamethyldisiloxane which replaces the hydrogen groups with methyl groups. Other common variations include the use of disiloxanes as bridges and spacers in larger compounds such as polymers.

References[edit]

(1) Sawama, Y.; Masuda, M.; Yasukawa, N.; Nakatani, R.; Nishimura, S.; Shibata, K.; Yamada, T.; Monguchi, Y.; Suzuka, H.; Takagi, Y.; Sajiki, H. The Journal of Organic Chemistry2016, 81, 4190-4195.

(2) DISILOXANE || Skin Deep® Cosmetics Database | EWG https://www.ewg.org/skindeep/ingredient/702127/DISILOXANE/#.WrUmb9PwZZp (accessed Mar 23, 2018).

(3) Disiloxane https://pubchem.ncbi.nlm.nih.gov/compound/Disiloxane (accessed Mar 23, 2018).

(4) Lassen, C.; Hansen, C.; Mikkelsen, S.; Maag, J. Siloxanes-Consumption, Toxicity, and Alternatives; Danish Ministry of the Environment, 2018.

(5) Almennigen, A.; Bastiansen, O.; Ewing, V.; Hedberg, K.; Tretteberg, M. ACTA Chemica Scandinavica 2018, 17, 2455-2460.

(6) Lord, R.; Robinson, D.; Schumb, W. Journal of the American Chemical Society 1956, 78, 1327-1332.

(7) Barrow, M.; Ebsworth, E.; Harding, M. Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry 1979, 35, 2093-2099.

(8) Varma, R.; MacDiarmid, A.; Miller, J. Inorganic Chemistry 1964, 3, 1754-1757.

(9) BOCK, H.; MOLLERE, P.; BECKER, G.; FRITZ, G. Chemischer Informationsdienst 1974, 5, 113-125.

(10) User, S. Cosmetic Fluids http://www.innospecinc.com/our-markets/performance-chemicals/personal-care/74-cosmetic-fluids-2 (accessed Mar 23, 2018).

(11) Disiloxane Ingredient Allergy Safety Information https://www.skinsafeproducts.com/ingredients/disiloxane (accessed Mar 23, 2018).

(12) Disiloxane | H6OSi2 | ChemSpider http://www.chemspider.com/Chemical-Structure.109921.html (accessed Mar 23, 2018).