Octamethylcyclotetrasiloxane
 | |
| Names | |
|---|---|
| Other names
D4, OMCTS | |
| Identifiers | |
| 556-67-2 | |
| Properties | |
| C8H24O4Si4 | |
| Molar mass | 296.62 |
| Density | 0.956 g/mL |
| Melting point | 17–18 °C |
| Boiling point | 175–176 °C |
| 56.2±2.5 ppb (23 °C) [1] | |
| Vapor pressure | 124.5±6.2 Pa (25 °C) [2] |
| Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | |
| Infobox references | |
Octamethylcyclotetrasiloxane, also called D4, is an organosilicon compound with the formula [(CH3)2SiO]4. lt is a colorless viscous liquid. It is a common cyclomethicone. Like other cyclomethicones, it is slightly volatile. It has attracted scrutiny because it is pervasive in the environment.[3]
Production
Commercially D4, is produced by cracking polysiloxanes. The silicone polymer equilibrated in the presence of strong base to give the tetamer:
- n/4 [(CH3)2SiO]n → n [(CH3)2SiO]4
The pentamer decamethylcyclopentasiloxane is also generated. These two cyclic species are separated from the polymer by distillation.[4]
Occurrence and environmental effects
It is among the most important of all the cyclic siloxanes, with a global production volume of 136·106 kilograms in 1993.[5]
As the smallest stable cyclic siloxane, D4 is one of the most abundant siloxanes in the environment, e.g. in landfill gases.[6]
Safety
D4 is toxic toward certain aquatic organisms. For mammals, it exhibits "toxic effects on various biological processes such as impaired fertility".[3]
References
- ↑ 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.
- ↑ Ying Duan Lei, Frank Wania, Dan Mathers (2010). "Temperature-Dependent Vapor Pressure of Selected Cyclic and Linear Polydimethylsiloxane Oligomers". Journal of Chemical & Engineering Data 55 (12): 5868–5873. doi:10.1021/je100835n.
- ↑ 3.0 3.1 Wang, De-Gao; Norwood, Warren; Alaee, Mehran; Byer, Jonathan D.; Brimble, Samantha "Review of Recent Advances in Research on the Toxicity, Detection, Occurrence and Fate of Cyclic Volatile Methyl Siloxanes in the Environment" Chemosphere 2013, volume 93, pages 711–725. doi:10.1016/j.chemosphere.2012.10.041
- ↑ Moretto, Hans-Heinrich; Schulze, Manfred; Wagner, Gebhard (2005). "Silicones". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a24_057.
- ↑ Philippe P. Quevauviller; Patrick Roose; Gert Verreet (24 August 2011). Chemical Marine Monitoring: Policy Framework and Analytical Trends. John Wiley & Sons. p. 2010. ISBN 978-1-119-97759-9.
- ↑ Franz-Bernd Frechen (2009). Odours and VOCs: Measurement, Regulation and Control Techniques. kassel university press GmbH. p. 287. ISBN 978-3-89958-609-1.