THE MECHANISM OF SOLVOLYSIS OF β-KETOSILANES

Article abstract of DOI:10.1016/0022-328X(85)88090-6

Rates of clevages of compounds of the type XC6H4COCH2SiR3 have been measured spectrophotometrically at various temperatures.The clevage of the Si-C bond occurs readily in THF/H2O alone but it is also catalyzed by NaOH.The effects of substituents X correlate with their Hammett ? constants (ρ=2.2 and 0.77 in the neutral and the basic medium, respectively).The rate isotope effect (r.i.e.), the effect of substitution at Si and the activation parameters are reported and dicussed.The data in the neutral medium are consistent with a cyclic mechanism in which transfer of a proton from a H2O molecule to the oxygen of the C=O is synchronous with the formation of the Si-O bond ad probably with the breaking of the C-Si bond, whereas in basic medium the most likely mechanism ivolves formation of a Si^v intermediate in the rate determining step of the reaction.