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| Names | |
|---|---|
| Other names
Methyl hydrogen siloxane; Poly(methyl siloxane); Poly(methylhydrosiloxane); Polysilicone 4
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| Identifiers | |
| Abbreviations | PMHS |
| ChemSpider |
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| ECHA InfoCard | 100.119.568 |
CompTox Dashboard (EPA)
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| Properties | |
| [CH3(H)SiO]n | |
| Molar mass | variable |
| Density | 1.006 g/cm3 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Polymethylhydrosiloxane (PMHS) is a polymer with the general structure [−CH3(H)Si−O−]. It is used in organic chemistry as a mild and stable reducing agent easily transferring hydrides to metal centers and a number of other reducible functional groups.[1][2] A variety of related materials are available under the following CAS registry numbers 9004-73-3, 16066-09-4, 63148-57-2, 178873-19-3. These include the tetramer ((MeSiHO)4), copolymers of dimethylsiloxane and methylhydrosiloxane, and trimethylsilyl terminated materials.
This material is prepared by the hydrolysis of monomethyldichlorosilane CAS#: 75-54-7:
- n MeSiHCl2 + n H2O → [MeSiHO]n + 2n HCl
The related polymer polydimethylsiloxane (PDMS) is made similarly, but lacking Si−H bonds, it exhibits no reducing properties. Dimethyldichlorosilane CAS#: 75-78-5 is then used instead of monomethyldichlorosilane CAS#: 75-54-7.
Illustrative of its use, PMHS is used for in situ conversion of tributyltin oxide to tributyltin hydride:[3]
- 2 MeSiH + (Bu3Sn)2O → Me2Si2O + 2 Bu3SnH