Problems of synthesis of tetrahedral organosilsesquioxanes. Hydrolytic condensation of hexafunctional branched organotetrasiloxanes
作者:E. A. Rebrov、N. A. Tebeneva、A. M. Mouzafarov、Yu. E. Ovchinnikov、Yu. T. Struchkov、T. V. Strelkova
DOI:10.1007/bf00700906
日期:1995.7
The hydrolytic condensation of methyltris(methyldichlorosiloxy)silane (Ib), methyl(la), and vinyltris(methyldiethoxysiloxy)silanes (Ic) in dilute homogeneous solutions was studied. It was found by X-ray diffraction and H-1 NMR methods that, irrespective of reaction conditions, only octaorganooctasilsesquioxanes (T-8), namely, octamethyloctasilsesquioxane and 1,4-divinylhexamethyloctasilsesquioxane, were obtained instead of the expected tetraorganotetrasilsesquioxanes (T-4). These data suggest that the condensation processes involved in the hydrolysis of 1a-c are predominantly intermolecular, and the molecules of the starting oligomers do not undergo rearrangements. Probably, the formation of T-4, whose molecules are built of four strained six-membered organosiloxane cycles, is less favorable thermodynamically than the formation of their homologs (T-8) built of eight-membered organosiloxane cycles.