Redistribution reactions silicon

In many cases, these cyclic siloxanes have to be removed from the system by distillation or fractionation, in order to obtain pure products. On the other hand, cyclic siloxanes where n = 3 and n = 4 are the two most important monomers used in the commercial production of various siloxane polymers or oligomers via the so-called equilibration or redistribution reactions which will be discussed in detail in Sect. 2.4. Therefore, in modern silicone technology, aqueous hydrolysis of chloro-silanes is usually employed for the preparation of cyclic siloxane monomers 122> more than for the direct synthesis of the (Si—X) functional oligomers. Equilibration reactions are the method of choice for the synthesis of functionally terminated siloxane oligomers. 

Reactions involving the exchange of substituents attached to silicon have been studied most extensively (186). Many monofunctional substituents bonded to silicon undergo redistribution reactions quite readily under... 

Tetraalkylsilanes also undergo redistribution reactions with silicon tetrafluoride (128) when heated in an autoclave at 300° to 400° C. Phenyl groups (225) redistribute readily with chlorine atoms on silicon when the... 

These redistribution reactions between metal-tin complexes not only provide extremely useful transition-metal-substituted organotin chlorides, but also demonstrate the chemical robustness of the M—Sn bonds. For example, whereas the W—Sn bond in [(CO)5WSnPh3] resists attack by dry HC1, the silicon and germanium analogs are cleaved to [C1W(C0)5] 49. 

Redistribution Reactions on Silicon Catalyzed by Transition Metal... 

The ease with which the tetrahalides dissociate thermally increases rapidly in the series from tetrafluoride to tetraiodide. While the chlorine-silicon bond ordinarily is not considered mobile, it undergoes an interesting redistribution reaction with the isocyanate bond in the preparation of chloroisocyanates of silicon.18... 

Besides, the hybrid silicones synthesized nsing the method in Scheme 3 produced scattered linear lines, whereas those obtained from precursor M mostly overlap on a single line, with a y intercept lower than 0.2 units compared to the PDMS one. This difference is typical of the theoretical lower hydrodynamic volumes for cyclic structures, compared to linear ones [21, 22]. From this analysis, it is reasonable to conclude that the formation of macrocycles prevents high molar masses to be reached, since the hybrid silicones are not capable of ring scission through redistribution reactions within the macromolecular chains, unless PDMS chains. 

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