Bis(trimethylsilyl)amine

Bis(trimethylsilyl)amine (also known as hexamethyldisilazane and HMDS) is an organosilicon compound with the molecular formula 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. Bis(trimethylsilyl)amine (also known as hexamethyldisilazane and HMDS) is an organosilicon compound with the molecular formula 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. Bis(trimethylsilyl)amine is prepared by treatment of trimethylsilyl chloride with ammonia: 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: Similarly to 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: 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 as an adhesion promoter for photoresist.Best results are obtained by applying HMDS from the gas phase on heated substrates.