Inductive effect silicon alkoxides

When alkyl-substituted silicon alkoxides are used, other factors such as inductive effects on reaction kinetics become more important. The desire for new hybrid materials has made sol-gel science and technology one of the faster growing areas of chemistry. Although much has been learned, there remains a need for a better chemical understanding of the complex sequence of reactions. 

Hydrolysis addresses the effects of processing parameters, such as catalysts, H2O Si ratio, and solvent, as well as steric and inductive factors on the mechanism of hydrolysis of silicon alkoxides and the reverse reaction, esterification. 

Silicon alkoxide condensation, 139-152 acid catalyzed, 148-150 base catalyzed, 145-148 catalyst effect, 140-142 effect of reverse reaction, 150-152 H20 Si effect, 197, 209 kinetics, 152-160 mechanism, 145-152 pH effect, 140-142, 197, 209 pressure effect, 147, 148 rate constant, 154, 160 solvent effect, 143-145 steric and inductive effects, 142, 143 Silicon alkoxide hydrolysis, 108, 109, 116-139,197 acid catalyzed, 131-134 base catalyzed, 134-136 effect of catalyst, 116-119 effect of fluorine, 118-119 effect of HjO.-Si, 123-127 kinetics, 118, 121-127, 152-160 mechanism, 116, 130-136 pressure effect, 134 rate constant, 154-155 solvent effect, 127-130 steric and inductive effects, 119-123 Silicon carbide-reinforced alumina, 865 Silicon carbide, 287-289, 736-737 Silicon cross-polarization NMR, 167-170, 220, 221... 

Different from water glass as a precursor, the Si—OR groups of silicon alkoxides must first be hydrolyzed before condensation reactions can take place. In addition to the inductive effects discussed above, the hydrolysis rates of alkoxysilanes are also influenced by steric factors. Any branching of the alkoxo group or increasing of the chain length lowers the hydrolysis rate of the alkoxysilanes. It means that the reaction rate decreases in the order Si(OMe)4 > Si(OEt)4 > Si(0"Pr)4> Si(0 Pr)4. 

Inductive effects of the BL may also influence the reactivity (similarly to the influence of groups R on the reactivity of silicon alkoxides discussed above). 

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