| Bis(trimethylsilyl)amine | |
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Bis(trimethylsilyl)amine |
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Other names
Hexamethyldisilazane |
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| Identifiers | |
| Abbreviations | HMDS |
| CAS number | 999-97-3 |
| PubChem | 13838, 18913873 amine, 45051731 sodium, 45051783 potassium |
| ChemSpider | 13238 |
| EC number | 213-668-5 |
| UN number | 2924, 3286 |
| MeSH | Hexamethylsilazane |
| RTECS number | JM9230000 |
| Beilstein Reference | 635752 |
| Jmol-3D images | Image 1 Image 2 |
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| Properties | |
| Molecular formula | C6H19NSi2 |
| Molar mass | 161.39 g mol−1 |
| Exact mass | 161.105602679 g mol-1 |
| Density | 0.77 g cm-3 |
| Melting point |
-78 °C, 195 K, -108 °F |
| Boiling point |
126 °C, 399 K, 259 °F |
| Hazards | |
| MSDS | External MSDS |
| NFPA 704 |
3
1
1
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| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Bis(trimethylsilyl)amine (also known as hexamethyldisilazane, or 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. This colorless liquid is a reagent and a precursor to bases that are popular in organic synthesis and organometallic chemistry.
Contents |
Bis(trimethylsilyl)amine is prepared by treatment of trimethylsilyl chloride with ammonia:[1]
The product is usually handled using air-free techniques since it hydrolyzes slowly in humid air.
Alkali metal bis(trimethylsilyl)amides result from the deprotonation of bis(trimethylsilyl)amine. For example lithium bis(trimethylsilyl)amide (LiHMDS) is prepared using n-butyllithium:
Together with sodium bis(trimethylsilyl)amide (NaHMDS) and potassium bis(trimethylsilyl)amide (KHMDS), LiHMDS is used as a non-nucleophilic base.
One of the uses of HMDS is as a reagent in condensation reactions of heterocyclic compounds such as in the microwave synthesis of a derivative of xanthine:[2]
HMDS can be used to convert alcohols into trimethylsilyl ethers. HMDS can be used to silylate laboratory glassware and make it hydrophobic, or automobile glass, just as Rain-X does.
In gas chromatography, HMDS can be used to silylate OH groups of organic compounds to increase volatility, this way enabling GC-analysis of chemicals that are otherwise non-volatile.
In photolithography, HMDS is often used in as an adhesion promoter for photoresist. Best results are obtained by applying HMDS from the gas phase on heated substrates.[3]
In electron microscopy, HMDS can be used as an alternative to critical point drying during sample preparation.[4]
In pyrolysis-gas chromatography-mass spectrometry, HMDS is added to the analyte to create sylilated diagnostic products during pyrolysis, in order to enhance detectability of compounds with polar functional groups.[5]