Hexamethyldisiloxane

Structural formula
Wedges to clarify the geometry
General
Surname	Hexamethyldisiloxane
other names	2,2,4,4-tetramethyl-3-oxa-2,4-disilapentane Bis (trimethylsilyl) ether HMDSO HMDS MM L 2
Molecular formula	C 6 H 18 OSi 2
Brief description	colorless liquid with a characteristic odor
External identifiers / databases
CAS number 107-46-0 EC number 203-492-7 ECHA InfoCard 100.003.176 PubChem 24764 Wikidata Q419440
properties
Molar mass	162.38 g mol −1
Physical state	liquid
density	0.76 g cm −3
Melting point	−59 ° C
boiling point	100 ° C
Vapor pressure	43 h Pa (20 ° C)
solubility	almost insoluble in water (930.7 ± 33.7 ppb at 23 ° C)
Refractive index	1.377
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 225-410 P: 210-233-240-273-403 + 235
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Hexamethyldisiloxane is a chemical compound from the group of siloxanes .

Extraction and presentation

Hexamethyldisiloxane is formed when chlorotrimethylsilane comes into contact with water, whereby chlorotrimethylsilane initially hydrolyzes in a violent reaction with evolution of heat and formation of hydrogen chloride to trimethylsilanol , which is unstable and condenses to hexamethyldisiloxane with elimination of water .

properties

The vapors of hexamethyldisiloxane can form an explosive mixture with air ( flash point −8 ° C, ignition temperature 310 ° C).

use

Hexamethyldisiloxane (like hexamethyldisilazane ) is used to produce quartz-like layers of silicon dioxide by plasma polymerisation or flame coating (e.g. for PET bottles). It is also used as a non-polar , low surface tension solvent (e.g. for drugs) and to introduce trimethylsilyl groups.

Hazard assessment

In 2012, hexamethyldisiloxane was included in the EU's ongoing action plan ( CoRAP ) in accordance with Regulation (EC) No. 1907/2006 (REACH) as part of substance evaluation . The effects of the substance on human health and the environment are re-evaluated and, if necessary, follow-up measures are initiated. The reasons for the uptake of hexamethyldisiloxane were concerns regarding consumer use and high (aggregated) tonnage as well as the dangers arising from a possible assignment to the group of CMR substances. The re-evaluation has been running since 2013 and is carried out by Norway . In order to be able to reach a final assessment, further information was requested.

See also

• Polydimethylsiloxane
• Octamethyltrisiloxane
• Decamethyltetrasiloxane

Individual evidence

1. ↑ ^{a b c d e f g} Entry on hexamethyldisiloxane in the GESTIS substance database of the IFA , accessed on March 11, 2015(JavaScript required) .
2. ↑ Sudarsanan Varaprath, Cecil L. Frye, Jerry Hamelink: Aqueous solubility of permethylsiloxanes (silicones). In: Environmental Toxicology and Chemistry . 15, 1996, pp. 1263-1265, doi: 10.1002 / etc.5620150803 .
3. ↑ Hexamethyldisiloxane data sheet from Sigma-Aldrich , accessed on May 13, 2017 ( PDF ).
4. ↑ INNOVENT Technologieentwicklung eV Jena: CCVD - Combustion Chemical Vapor Deposition ( Memento of the original from February 25, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . 
5. ↑ R. Weidl, B. Zobel, A. Heft, A. Pfuch, U. lattice, B. Grünler, T. Richter, C. Erbe: Atmospheric pressure C-CVD coating processes - trends and developments. In: Electroplating . 2007, 8, pp. 1978-1982.
6. ↑ Uni-Bochum: P. Awakowicz M. Deilmann: Plasma sterilization of PET bottles: tight and sterile in a double pack (pdf)
7. ↑ Nitrochemie: Treatment solution ( Memento from September 11, 2012 in the web archive archive.today ).
8. ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): Hexamethyldisiloxane , accessed on March 26, 2019.