Organofunctional silanes synthesis

The synthesis of organosilicones and organosilicone surfactants has been well described elsewhere [36-39] and hence only a brief review is given here. Industrially the manufacture of silicones is performed stepwise via the alkylchlorosilanes, produced through the reaction of elemental silicon with methyl chloride (the Muller—Rochow Process) [40,41]. Inclusion of HC1 and/or H2(g) into the reaction mixture, as in Eq. (1.2), yields CH3HSiCl2, the precursor to the organofunctional silanes, and therefore the silicone surfactants ... 

We have now succeeded in the development of two new methods for the preparation of organofunctional silanes, both involving electroreductive coupling. The first synthesis concept comprises the anionic cleavage of electrochemically formed disilanes and subsequent reaction with organic halides, whereas the second even more general route involves the direct electrochemical Si-C bond formation. 

Organohydrogensilanes are formed as byproducts in the direct synthesis of dimethyldichlorosilane (see Section 4.2.1) and are important in the manufacture of hydrogen-containing siloxanes and organofunctional silanes (see... 

The usual way of preparing such aminopropyl-terminated siloxanes is the synthesis via a base-catalyzed equilibration reaction [1, 2]. A more convenient way is the termination reaction of silanol-terminated siloxanes with special organofunctional silanes [3,4],... 

The incorporation of organofunctional groups on the silica surface may be effectuated during the synthesis of the silica material. The addition of organofunctional alkoxysilanes to the TEOS solution in the sol-gel process, produces functionalized silica gels. This procedure does not allow a careful control of the obtained surface morphology. Since the relative amounts of silane and TEOS is the only variable parameter, neither layer thickness, nor modification density can be precisely tuned. This results in an irreproducible functionalization of the surface. 

Just as the hydrosilylation reaction is important in the synthesis of silanes, so it also serves as a useful route to functional polysiloxanes. The same variety of chemistry as previously described for silanes is available and two further examples are given in equations 82 and 83. One of the main advantages of this route is that the silicon hydride prepolymers are well characterized and readily available materials, which in turn leads to well-defined organofunctional products. A disadvantage is the low efficiency in the use of the precious metal catalyst and the difficulty of its recovery. This is particularly true for systems containing a low level of functionality but this can be partially overcome by using recyclable platinum catalysts on solid supports216,217. 

Organofunctional epoxysilanes may be prepared by hydrosilylating unsaturated epoxides or epoxidized unsaturated silanes. The hydrosilylation of allyl ethers CH2=CHCH20R is commonly used for synthesis (e.g., y-glycidoxytrimethoxysilane) as follows ... 

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