Silazanes hexamethyldisilazane

The most important representative of the silazanes is hexamethyldisilazane, which is utilized in large quantities for the introduction of protective groups in the synthesis of pharmaceuticals and for hydrophobizing fillers, in particular silicates. It can be easily produced by reacting trimethylchlorosilane with ammonia ... 

Borazine-based Si/B/N/C polymers have been obtained by polycondensing H3N3B3(Cl)2Si(SiMe3)3 with hexamethyldisilazane [88]. Here once again silazane cleavage, forming the volatile chlorotrimethylsilane as a byproduct, is the driving process. 

Instead of the chlorosilanes, other reactive silanes can be used as well. Alkoxysilanes are less reactive than chlorosilanes, but will form bonded phases in the presence of acidic or basic catalysts. Silazanes, on the other hand, are as reactive or more reactive than chlorosilanes. A well-known example is the reaction of the silica surface with hexamethyldisilazane ... 

Summary Reactions of free methyl cations with diisobutylamine (1), isobutylaminotrimethylsilane (2) and hexamethyldisilazane (3) were studied by the radiochemical method. It was shown that in all cases studied, the proton transfer is a predominant channel. Probabilities for the reaction to enter this channel are 0.87 for 1, 0.67 for 2 and 0.93 for 3. The last value contradicts the well-known dependence of the lowering of the proton affinity of amines upon the CHa/SiHa ratio. However, quantum chemical calculations have shown that the interaction of the silazane HOMO with the CHa LUMO is symmetry forbidden. This fact may result in the lowering of the methyl cation affinity for silazanes and preference for the proton transfer channel. 

Fumed silica, or fumed silicon dioxide, is produced by the vapor phase hydrolysis of silicon tetrachloride in an H2/O2 flame. The reactions are shovm in Chapter 19. Hydrophilic fumed silica bearing hydroxyl groups on its surface is produced by this process. Hydrophobic fumed silica is made by processing fumed hydrophilic silica through in-line hydrophobic treatments such as with silanes, siloxanes, silazanes, and so on [1]. Examples of different types of hydrophobic fumed silica coatings include DMDS (dimethyldichlorosilane), TMOS (trimethoxyoctylsilane), HMDS (hexamethyldisilazane). 

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