Bis(trimethylsilyl)amine
- Hexamethyldisilazane
- HMDS
- Bis (trimethylsilyl ) amine
Colorless liquid
Liquid
0.78 g · cm -3 ( 20 ° C)
-82 ° C
126 ° C.
20 hPa ( 20 ° C)
Decomposes in water
From 1.4069 to 1.4089
Risk
Template: Infobox chemical / molecular formula search available
Hexamethyldisilazane HMDS short, molecular formula C6H19NSi2, is widely used for the surface modification of solid surfaces, such as silica particles or for imparting water repellency to improve the adhesion of photoresists on semiconductor surfaces. In the semiconductor industry, the method of chemical vapor deposition ( CVD engl. ) allows a simple application of HMDS.
In organic chemistry, hexamethyldisilazane is used inter alia for the introduction of trimethylsilyl groups. Compared with chlorotrimethylsilane, the handling is more comfortable because hexamethyldisilazane is quite insensitive to water or humidity. Also possible to dispense with the addition of an auxiliary base such as ammonia in the silylation occurs only as a by- product. For most, a higher reaction temperature must be applied, which can be a disadvantage for sensitive substrates.
Production and representation
Hexamethyldisilazane can be obtained by reaction of trimethylsilyl chloride with ammonia.
Properties
Hexamethyldisilazane is a colorless to yellow liquid with an amine-like odor, which is highly flammable. The compound has a flash point below 15 ° C. The explosion range is between 0.8 vol% as the lower explosive limit ( LEL) and 25.9 vol - % as the upper explosive limit ( UEL). The ignition temperature is 325 ° C. The fabric falls within the temperature class T2. Moisture carried a slow hydrolysis with the formation of hexamethyldisiloxane and ammonia. Upon contact with water, the compound is first hydrolyzed in a violent exothermic reaction and formation of ammonia to trimethylsilanol, which is unstable and elimination of water to the water- hexamethyldisiloxane ( bis ( trimethylsilyl) ether) condensed. The heat of hydrolysis is -144.4 kJ · mol -1.
Health hazards
The effects of hexamethyldisilazane on human health and the environment are tested under REACH in 2014 as part of the fabric rating of Spain.